Split {,local-}derivation-goal.{cc,hh}

This separates the scheduling logic (including simple hook pathway) from
the local-store needing code.

This should be the final split for now. I'm reasonably happy with how
it's turning out, even before I'm done moving code into
`local-derivation-goal`. Benefits:

1. This will help "witness" that the hook case is indeed a lot simpler,
   and also compensate for the increased complexity that comes from
   content-addressed derivation outputs.

2. It also moves us ever so slightly towards a world where we could use
   off-the-shelf storage or sandboxing, since `local-derivation-goal`
   would be gutted in those cases, but `derivation-goal` should remain
   nearly the same.

The new `#if 0` in the new files will be deleted in the following
commit. I keep it here so if it turns out more stuff can be moved over,
it's easy to do so in a way that preserves ordering --- and thus
prevents conflicts.

N.B.
```sh
git diff HEAD^^ --color-moved --find-copies-harder --patience --stat
```
makes nicer output.

7 files changed, 327 insertions, 3043 deletions

diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 924c69fb7..c29237f5c 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -9,10 +9,10 @@
 #include "archive.hh"
 #include "json.hh"
 #include "compression.hh"
-#include "daemon.hh"
 #include "worker-protocol.hh"
 #include "topo-sort.hh"
 #include "callback.hh"
+#include "local-store.hh" // TODO remove, along with remaining downcasts
 
 #include <regex>
 #include <queue>
@@ -62,40 +62,6 @@
 
 namespace nix {
 
-void handleDiffHook(
-    uid_t uid, uid_t gid,
-    const Path & tryA, const Path & tryB,
-    const Path & drvPath, const Path & tmpDir)
-{
-    auto diffHook = settings.diffHook;
-    if (diffHook != "" && settings.runDiffHook) {
-        try {
-            RunOptions diffHookOptions(diffHook,{tryA, tryB, drvPath, tmpDir});
-            diffHookOptions.searchPath = true;
-            diffHookOptions.uid = uid;
-            diffHookOptions.gid = gid;
-            diffHookOptions.chdir = "/";
-
-            auto diffRes = runProgram(diffHookOptions);
-            if (!statusOk(diffRes.first))
-                throw ExecError(diffRes.first,
-                    "diff-hook program '%1%' %2%",
-                    diffHook,
-                    statusToString(diffRes.first));
-
-            if (diffRes.second != "")
-                printError(chomp(diffRes.second));
-        } catch (Error & error) {
-            ErrorInfo ei = error.info();
-            // FIXME: wrap errors.
-            ei.msg = hintfmt("diff hook execution failed: %s", ei.msg.str());
-            logError(ei);
-        }
-    }
-}
-
-const Path DerivationGoal::homeDir = "/homeless-shelter";
-
 DerivationGoal::DerivationGoal(const StorePath & drvPath,
     const StringSet & wantedOutputs, Worker & worker, BuildMode buildMode)
     : Goal(worker)
@@ -144,9 +110,6 @@ DerivationGoal::~DerivationGoal()
 {
     /* Careful: we should never ever throw an exception from a
        destructor. */
-    try { killChild(); } catch (...) { ignoreException(); }
-    try { stopDaemon(); } catch (...) { ignoreException(); }
-    try { deleteTmpDir(false); } catch (...) { ignoreException(); }
     try { closeLogFile(); } catch (...) { ignoreException(); }
 }
 
@@ -161,38 +124,8 @@ string DerivationGoal::key()
 }
 
 
-inline bool DerivationGoal::needsHashRewrite()
-{
-#if __linux__
-    return !useChroot;
-#else
-    /* Darwin requires hash rewriting even when sandboxing is enabled. */
-    return true;
-#endif
-}
-
-
 void DerivationGoal::killChild()
 {
-    if (pid != -1) {
-        worker.childTerminated(this);
-
-        if (buildUser) {
-            /* If we're using a build user, then there is a tricky
-               race condition: if we kill the build user before the
-               child has done its setuid() to the build user uid, then
-               it won't be killed, and we'll potentially lock up in
-               pid.wait().  So also send a conventional kill to the
-               child. */
-            ::kill(-pid, SIGKILL); /* ignore the result */
-            buildUser->kill();
-            pid.wait();
-        } else
-            pid.kill();
-
-        assert(pid == -1);
-    }
-
     hook.reset();
 }
 
@@ -697,64 +630,10 @@ void DerivationGoal::tryToBuild()
 }
 
 void DerivationGoal::tryLocalBuild() {
-    /* Make sure that we are allowed to start a build. */
-    if (!dynamic_cast<LocalStore *>(&worker.store)) {
-        throw Error(
-            "unable to build with a primary store that isn't a local store; "
-            "either pass a different '--store' or enable remote builds."
-            "\nhttps://nixos.org/nix/manual/#chap-distributed-builds");
-    }
-    unsigned int curBuilds = worker.getNrLocalBuilds();
-    if (curBuilds >= settings.maxBuildJobs) {
-        worker.waitForBuildSlot(shared_from_this());
-        outputLocks.unlock();
-        return;
-    }
-
-    /* If `build-users-group' is not empty, then we have to build as
-       one of the members of that group. */
-    if (settings.buildUsersGroup != "" && getuid() == 0) {
-#if defined(__linux__) || defined(__APPLE__)
-        if (!buildUser) buildUser = std::make_unique<UserLock>();
-
-        if (buildUser->findFreeUser()) {
-            /* Make sure that no other processes are executing under this
-               uid. */
-            buildUser->kill();
-        } else {
-            if (!actLock)
-                actLock = std::make_unique<Activity>(*logger, lvlWarn, actBuildWaiting,
-                    fmt("waiting for UID to build '%s'", yellowtxt(worker.store.printStorePath(drvPath))));
-            worker.waitForAWhile(shared_from_this());
-            return;
-        }
-#else
-        /* Don't know how to block the creation of setuid/setgid
-           binaries on this platform. */
-        throw Error("build users are not supported on this platform for security reasons");
-#endif
-    }
-
-    actLock.reset();
-
-    try {
-
-        /* Okay, we have to build. */
-        startBuilder();
-
-    } catch (BuildError & e) {
-        outputLocks.unlock();
-        buildUser.reset();
-        worker.permanentFailure = true;
-        done(BuildResult::InputRejected, e);
-        return;
-    }
-
-    /* This state will be reached when we get EOF on the child's
-       log pipe. */
-    state = &DerivationGoal::buildDone;
-
-    started();
+    throw Error(
+        "unable to build with a primary store that isn't a local store; "
+        "either pass a different '--store' or enable remote builds."
+        "\nhttps://nixos.org/nix/manual/#chap-distributed-builds");
 }
 
 
@@ -811,25 +690,63 @@ void replaceValidPath(const Path & storePath, const Path & tmpPath)
 }
 
 
-MakeError(NotDeterministic, BuildError);
+int DerivationGoal::getChildStatus()
+{
+    return hook->pid.kill();
+}
+
+
+void DerivationGoal::closeReadPipes()
+{
+    hook->builderOut.readSide = -1;
+    hook->fromHook.readSide = -1;
+}
+
+
+void DerivationGoal::cleanupHookFinally()
+{
+}
+
+
+void DerivationGoal::cleanupPreChildKill()
+{
+}
+
+
+void DerivationGoal::cleanupPostChildKill()
+{
+}
+
+
+bool DerivationGoal::cleanupDecideWhetherDiskFull()
+{
+    return false;
+}
+
+
+void DerivationGoal::cleanupPostOutputsRegisteredModeCheck()
+{
+}
+
+
+void DerivationGoal::cleanupPostOutputsRegisteredModeNonCheck()
+{
+}
 
 
 void DerivationGoal::buildDone()
 {
     trace("build done");
 
-    /* Release the build user at the end of this function. We don't do
-       it right away because we don't want another build grabbing this
-       uid and then messing around with our output. */
-    Finally releaseBuildUser([&]() { buildUser.reset(); });
+    Finally releaseBuildUser([&](){ this->cleanupHookFinally(); });
 
-    sandboxMountNamespace = -1;
+    cleanupPreChildKill();
 
     /* Since we got an EOF on the logger pipe, the builder is presumed
        to have terminated.  In fact, the builder could also have
        simply have closed its end of the pipe, so just to be sure,
        kill it. */
-    int status = hook ? hook->pid.kill() : pid.kill();
+    int status = getChildStatus();
 
     debug("builder process for '%s' finished", worker.store.printStorePath(drvPath));
 
@@ -840,24 +757,12 @@ void DerivationGoal::buildDone()
     worker.childTerminated(this);
 
     /* Close the read side of the logger pipe. */
-    if (hook) {
-        hook->builderOut.readSide = -1;
-        hook->fromHook.readSide = -1;
-    } else
-        builderOut.readSide = -1;
+    closeReadPipes();
 
     /* Close the log file. */
     closeLogFile();
 
-    /* When running under a build user, make sure that all processes
-       running under that uid are gone.  This is to prevent a
-       malicious user from leaving behind a process that keeps files
-       open and modifies them after they have been chown'ed to
-       root. */
-    if (buildUser) buildUser->kill();
-
-    /* Terminate the recursive Nix daemon. */
-    stopDaemon();
+    cleanupPostChildKill();
 
     bool diskFull = false;
 
@@ -866,36 +771,7 @@ void DerivationGoal::buildDone()
         /* Check the exit status. */
         if (!statusOk(status)) {
 
-            /* Heuristically check whether the build failure may have
-               been caused by a disk full condition.  We have no way
-               of knowing whether the build actually got an ENOSPC.
-               So instead, check if the disk is (nearly) full now.  If
-               so, we don't mark this build as a permanent failure. */
-#if HAVE_STATVFS
-            if (auto localStore = dynamic_cast<LocalStore *>(&worker.store)) {
-                uint64_t required = 8ULL * 1024 * 1024; // FIXME: make configurable
-                struct statvfs st;
-                if (statvfs(localStore->realStoreDir.c_str(), &st) == 0 &&
-                    (uint64_t) st.f_bavail * st.f_bsize < required)
-                    diskFull = true;
-                if (statvfs(tmpDir.c_str(), &st) == 0 &&
-                    (uint64_t) st.f_bavail * st.f_bsize < required)
-                    diskFull = true;
-            }
-#endif
-
-            deleteTmpDir(false);
-
-            /* Move paths out of the chroot for easier debugging of
-               build failures. */
-            if (useChroot && buildMode == bmNormal)
-                for (auto & [_, status] : initialOutputs) {
-                    if (!status.known) continue;
-                    if (buildMode != bmCheck && status.known->isValid()) continue;
-                    auto p = worker.store.printStorePath(status.known->path);
-                    if (pathExists(chrootRootDir + p))
-                        rename((chrootRootDir + p).c_str(), p.c_str());
-                }
+            diskFull |= cleanupDecideWhetherDiskFull();
 
             auto msg = fmt("builder for '%s' %s",
                 yellowtxt(worker.store.printStorePath(drvPath)),
@@ -975,19 +851,12 @@ void DerivationGoal::buildDone()
         }
 
         if (buildMode == bmCheck) {
-            deleteTmpDir(true);
+            cleanupPostOutputsRegisteredModeCheck();
             done(BuildResult::Built);
             return;
         }
 
-        /* Delete unused redirected outputs (when doing hash rewriting). */
-        for (auto & i : redirectedOutputs)
-            deletePath(worker.store.Store::toRealPath(i.second));
-
-        /* Delete the chroot (if we were using one). */
-        autoDelChroot.reset(); /* this runs the destructor */
-
-        deleteTmpDir(true);
+        cleanupPostOutputsRegisteredModeNonCheck();
 
         /* Repeat the build if necessary. */
         if (curRound++ < nrRounds) {
@@ -1171,13 +1040,6 @@ HookReply DerivationGoal::tryBuildHook()
 }
 
 
-int childEntry(void * arg)
-{
-    ((DerivationGoal *) arg)->runChild();
-    return 1;
-}
-
-
 StorePathSet DerivationGoal::exportReferences(const StorePathSet & storePaths)
 {
     StorePathSet paths;
@@ -1213,1769 +1075,6 @@ StorePathSet DerivationGoal::exportReferences(const StorePathSet & storePaths)
     return paths;
 }
 
-static std::once_flag dns_resolve_flag;
-
-static void preloadNSS() {
-    /* builtin:fetchurl can trigger a DNS lookup, which with glibc can trigger a dynamic library load of
-       one of the glibc NSS libraries in a sandboxed child, which will fail unless the library's already
-       been loaded in the parent. So we force a lookup of an invalid domain to force the NSS machinery to
-       load its lookup libraries in the parent before any child gets a chance to. */
-    std::call_once(dns_resolve_flag, []() {
-        struct addrinfo *res = NULL;
-
-        if (getaddrinfo("this.pre-initializes.the.dns.resolvers.invalid.", "http", NULL, &res) != 0) {
-            if (res) freeaddrinfo(res);
-        }
-    });
-}
-
-
-void linkOrCopy(const Path & from, const Path & to)
-{
-    if (link(from.c_str(), to.c_str()) == -1) {
-        /* Hard-linking fails if we exceed the maximum link count on a
-           file (e.g. 32000 of ext3), which is quite possible after a
-           'nix-store --optimise'. FIXME: actually, why don't we just
-           bind-mount in this case?
-
-           It can also fail with EPERM in BeegFS v7 and earlier versions
-           which don't allow hard-links to other directories */
-        if (errno != EMLINK && errno != EPERM)
-            throw SysError("linking '%s' to '%s'", to, from);
-        copyPath(from, to);
-    }
-}
-
-
-void DerivationGoal::startBuilder()
-{
-    /* Right platform? */
-    if (!parsedDrv->canBuildLocally(worker.store))
-        throw Error("a '%s' with features {%s} is required to build '%s', but I am a '%s' with features {%s}",
-            drv->platform,
-            concatStringsSep(", ", parsedDrv->getRequiredSystemFeatures()),
-            worker.store.printStorePath(drvPath),
-            settings.thisSystem,
-            concatStringsSep<StringSet>(", ", worker.store.systemFeatures));
-
-    if (drv->isBuiltin())
-        preloadNSS();
-
-#if __APPLE__
-    additionalSandboxProfile = parsedDrv->getStringAttr("__sandboxProfile").value_or("");
-#endif
-
-    /* Are we doing a chroot build? */
-    {
-        auto noChroot = parsedDrv->getBoolAttr("__noChroot");
-        if (settings.sandboxMode == smEnabled) {
-            if (noChroot)
-                throw Error("derivation '%s' has '__noChroot' set, "
-                    "but that's not allowed when 'sandbox' is 'true'", worker.store.printStorePath(drvPath));
-#if __APPLE__
-            if (additionalSandboxProfile != "")
-                throw Error("derivation '%s' specifies a sandbox profile, "
-                    "but this is only allowed when 'sandbox' is 'relaxed'", worker.store.printStorePath(drvPath));
-#endif
-            useChroot = true;
-        }
-        else if (settings.sandboxMode == smDisabled)
-            useChroot = false;
-        else if (settings.sandboxMode == smRelaxed)
-            useChroot = !(derivationIsImpure(derivationType)) && !noChroot;
-    }
-
-    if (auto localStoreP = dynamic_cast<LocalStore *>(&worker.store)) {
-        auto & localStore = *localStoreP;
-        if (localStore.storeDir != localStore.realStoreDir) {
-            #if __linux__
-                useChroot = true;
-            #else
-                throw Error("building using a diverted store is not supported on this platform");
-            #endif
-        }
-    }
-
-    /* Create a temporary directory where the build will take
-       place. */
-    tmpDir = createTempDir("", "nix-build-" + std::string(drvPath.name()), false, false, 0700);
-
-    chownToBuilder(tmpDir);
-
-    for (auto & [outputName, status] : initialOutputs) {
-        /* Set scratch path we'll actually use during the build.
-
-           If we're not doing a chroot build, but we have some valid
-           output paths.  Since we can't just overwrite or delete
-           them, we have to do hash rewriting: i.e. in the
-           environment/arguments passed to the build, we replace the
-           hashes of the valid outputs with unique dummy strings;
-           after the build, we discard the redirected outputs
-           corresponding to the valid outputs, and rewrite the
-           contents of the new outputs to replace the dummy strings
-           with the actual hashes. */
-        auto scratchPath =
-            !status.known
-                ? makeFallbackPath(outputName)
-            : !needsHashRewrite()
-                /* Can always use original path in sandbox */
-                ? status.known->path
-            : !status.known->isPresent()
-                /* If path doesn't yet exist can just use it */
-                ? status.known->path
-            : buildMode != bmRepair && !status.known->isValid()
-                /* If we aren't repairing we'll delete a corrupted path, so we
-                   can use original path */
-                ? status.known->path
-            :   /* If we are repairing or the path is totally valid, we'll need
-                   to use a temporary path */
-                makeFallbackPath(status.known->path);
-        scratchOutputs.insert_or_assign(outputName, scratchPath);
-
-        /* A non-removed corrupted path needs to be stored here, too */
-        if (buildMode == bmRepair && !status.known->isValid())
-            redirectedBadOutputs.insert(status.known->path);
-
-        /* Substitute output placeholders with the scratch output paths.
-           We'll use during the build. */
-        inputRewrites[hashPlaceholder(outputName)] = worker.store.printStorePath(scratchPath);
-
-        /* Additional tasks if we know the final path a priori. */
-        if (!status.known) continue;
-        auto fixedFinalPath = status.known->path;
-
-        /* Additional tasks if the final and scratch are both known and
-           differ. */
-        if (fixedFinalPath == scratchPath) continue;
-
-        /* Ensure scratch path is ours to use. */
-        deletePath(worker.store.printStorePath(scratchPath));
-
-        /* Rewrite and unrewrite paths */
-        {
-            std::string h1 { fixedFinalPath.hashPart() };
-            std::string h2 { scratchPath.hashPart() };
-            inputRewrites[h1] = h2;
-        }
-
-        redirectedOutputs.insert_or_assign(std::move(fixedFinalPath), std::move(scratchPath));
-    }
-
-    /* Construct the environment passed to the builder. */
-    initEnv();
-
-    writeStructuredAttrs();
-
-    /* Handle exportReferencesGraph(), if set. */
-    if (!parsedDrv->getStructuredAttrs()) {
-        /* The `exportReferencesGraph' feature allows the references graph
-           to be passed to a builder.  This attribute should be a list of
-           pairs [name1 path1 name2 path2 ...].  The references graph of
-           each `pathN' will be stored in a text file `nameN' in the
-           temporary build directory.  The text files have the format used
-           by `nix-store --register-validity'.  However, the deriver
-           fields are left empty. */
-        string s = get(drv->env, "exportReferencesGraph").value_or("");
-        Strings ss = tokenizeString<Strings>(s);
-        if (ss.size() % 2 != 0)
-            throw BuildError("odd number of tokens in 'exportReferencesGraph': '%1%'", s);
-        for (Strings::iterator i = ss.begin(); i != ss.end(); ) {
-            string fileName = *i++;
-            static std::regex regex("[A-Za-z_][A-Za-z0-9_.-]*");
-            if (!std::regex_match(fileName, regex))
-                throw Error("invalid file name '%s' in 'exportReferencesGraph'", fileName);
-
-            auto storePathS = *i++;
-            if (!worker.store.isInStore(storePathS))
-                throw BuildError("'exportReferencesGraph' contains a non-store path '%1%'", storePathS);
-            auto storePath = worker.store.toStorePath(storePathS).first;
-
-            /* Write closure info to <fileName>. */
-            writeFile(tmpDir + "/" + fileName,
-                worker.store.makeValidityRegistration(
-                    exportReferences({storePath}), false, false));
-        }
-    }
-
-    if (useChroot) {
-
-        /* Allow a user-configurable set of directories from the
-           host file system. */
-        dirsInChroot.clear();
-
-        for (auto i : settings.sandboxPaths.get()) {
-            if (i.empty()) continue;
-            bool optional = false;
-            if (i[i.size() - 1] == '?') {
-                optional = true;
-                i.pop_back();
-            }
-            size_t p = i.find('=');
-            if (p == string::npos)
-                dirsInChroot[i] = {i, optional};
-            else
-                dirsInChroot[string(i, 0, p)] = {string(i, p + 1), optional};
-        }
-        dirsInChroot[tmpDirInSandbox] = tmpDir;
-
-        /* Add the closure of store paths to the chroot. */
-        StorePathSet closure;
-        for (auto & i : dirsInChroot)
-            try {
-                if (worker.store.isInStore(i.second.source))
-                    worker.store.computeFSClosure(worker.store.toStorePath(i.second.source).first, closure);
-            } catch (InvalidPath & e) {
-            } catch (Error & e) {
-                e.addTrace({}, "while processing 'sandbox-paths'");
-                throw;
-            }
-        for (auto & i : closure) {
-            auto p = worker.store.printStorePath(i);
-            dirsInChroot.insert_or_assign(p, p);
-        }
-
-        PathSet allowedPaths = settings.allowedImpureHostPrefixes;
-
-        /* This works like the above, except on a per-derivation level */
-        auto impurePaths = parsedDrv->getStringsAttr("__impureHostDeps").value_or(Strings());
-
-        for (auto & i : impurePaths) {
-            bool found = false;
-            /* Note: we're not resolving symlinks here to prevent
-               giving a non-root user info about inaccessible
-               files. */
-            Path canonI = canonPath(i);
-            /* If only we had a trie to do this more efficiently :) luckily, these are generally going to be pretty small */
-            for (auto & a : allowedPaths) {
-                Path canonA = canonPath(a);
-                if (canonI == canonA || isInDir(canonI, canonA)) {
-                    found = true;
-                    break;
-                }
-            }
-            if (!found)
-                throw Error("derivation '%s' requested impure path '%s', but it was not in allowed-impure-host-deps",
-                    worker.store.printStorePath(drvPath), i);
-
-            dirsInChroot[i] = i;
-        }
-
-#if __linux__
-        /* Create a temporary directory in which we set up the chroot
-           environment using bind-mounts.  We put it in the Nix store
-           to ensure that we can create hard-links to non-directory
-           inputs in the fake Nix store in the chroot (see below). */
-        chrootRootDir = worker.store.Store::toRealPath(drvPath) + ".chroot";
-        deletePath(chrootRootDir);
-
-        /* Clean up the chroot directory automatically. */
-        autoDelChroot = std::make_shared<AutoDelete>(chrootRootDir);
-
-        printMsg(lvlChatty, format("setting up chroot environment in '%1%'") % chrootRootDir);
-
-        if (mkdir(chrootRootDir.c_str(), 0750) == -1)
-            throw SysError("cannot create '%1%'", chrootRootDir);
-
-        if (buildUser && chown(chrootRootDir.c_str(), 0, buildUser->getGID()) == -1)
-            throw SysError("cannot change ownership of '%1%'", chrootRootDir);
-
-        /* Create a writable /tmp in the chroot.  Many builders need
-           this.  (Of course they should really respect $TMPDIR
-           instead.) */
-        Path chrootTmpDir = chrootRootDir + "/tmp";
-        createDirs(chrootTmpDir);
-        chmod_(chrootTmpDir, 01777);
-
-        /* Create a /etc/passwd with entries for the build user and the
-           nobody account.  The latter is kind of a hack to support
-           Samba-in-QEMU. */
-        createDirs(chrootRootDir + "/etc");
-
-        /* Declare the build user's group so that programs get a consistent
-           view of the system (e.g., "id -gn"). */
-        writeFile(chrootRootDir + "/etc/group",
-            fmt("root:x:0:\n"
-                "nixbld:!:%1%:\n"
-                "nogroup:x:65534:\n", sandboxGid()));
-
-        /* Create /etc/hosts with localhost entry. */
-        if (!(derivationIsImpure(derivationType)))
-            writeFile(chrootRootDir + "/etc/hosts", "127.0.0.1 localhost\n::1 localhost\n");
-
-        /* Make the closure of the inputs available in the chroot,
-           rather than the whole Nix store.  This prevents any access
-           to undeclared dependencies.  Directories are bind-mounted,
-           while other inputs are hard-linked (since only directories
-           can be bind-mounted).  !!! As an extra security
-           precaution, make the fake Nix store only writable by the
-           build user. */
-        Path chrootStoreDir = chrootRootDir + worker.store.storeDir;
-        createDirs(chrootStoreDir);
-        chmod_(chrootStoreDir, 01775);
-
-        if (buildUser && chown(chrootStoreDir.c_str(), 0, buildUser->getGID()) == -1)
-            throw SysError("cannot change ownership of '%1%'", chrootStoreDir);
-
-        for (auto & i : inputPaths) {
-            auto p = worker.store.printStorePath(i);
-            Path r = worker.store.toRealPath(p);
-            if (S_ISDIR(lstat(r).st_mode))
-                dirsInChroot.insert_or_assign(p, r);
-            else
-                linkOrCopy(r, chrootRootDir + p);
-        }
-
-        /* If we're repairing, checking or rebuilding part of a
-           multiple-outputs derivation, it's possible that we're
-           rebuilding a path that is in settings.dirsInChroot
-           (typically the dependencies of /bin/sh).  Throw them
-           out. */
-        for (auto & i : drv->outputsAndOptPaths(worker.store)) {
-            /* If the name isn't known a priori (i.e. floating
-               content-addressed derivation), the temporary location we use
-               should be fresh.  Freshness means it is impossible that the path
-               is already in the sandbox, so we don't need to worry about
-               removing it.  */
-            if (i.second.second)
-                dirsInChroot.erase(worker.store.printStorePath(*i.second.second));
-        }
-
-#elif __APPLE__
-        /* We don't really have any parent prep work to do (yet?)
-           All work happens in the child, instead. */
-#else
-        throw Error("sandboxing builds is not supported on this platform");
-#endif
-    }
-
-    if (needsHashRewrite() && pathExists(homeDir))
-        throw Error("home directory '%1%' exists; please remove it to assure purity of builds without sandboxing", homeDir);
-
-    if (useChroot && settings.preBuildHook != "" && dynamic_cast<Derivation *>(drv.get())) {
-        printMsg(lvlChatty, format("executing pre-build hook '%1%'")
-            % settings.preBuildHook);
-        auto args = useChroot ? Strings({worker.store.printStorePath(drvPath), chrootRootDir}) :
-            Strings({ worker.store.printStorePath(drvPath) });
-        enum BuildHookState {
-            stBegin,
-            stExtraChrootDirs
-        };
-        auto state = stBegin;
-        auto lines = runProgram(settings.preBuildHook, false, args);
-        auto lastPos = std::string::size_type{0};
-        for (auto nlPos = lines.find('\n'); nlPos != string::npos;
-                nlPos = lines.find('\n', lastPos)) {
-            auto line = std::string{lines, lastPos, nlPos - lastPos};
-            lastPos = nlPos + 1;
-            if (state == stBegin) {
-                if (line == "extra-sandbox-paths" || line == "extra-chroot-dirs") {
-                    state = stExtraChrootDirs;
-                } else {
-                    throw Error("unknown pre-build hook command '%1%'", line);
-                }
-            } else if (state == stExtraChrootDirs) {
-                if (line == "") {
-                    state = stBegin;
-                } else {
-                    auto p = line.find('=');
-                    if (p == string::npos)
-                        dirsInChroot[line] = line;
-                    else
-                        dirsInChroot[string(line, 0, p)] = string(line, p + 1);
-                }
-            }
-        }
-    }
-
-    /* Fire up a Nix daemon to process recursive Nix calls from the
-       builder. */
-    if (parsedDrv->getRequiredSystemFeatures().count("recursive-nix"))
-        startDaemon();
-
-    /* Run the builder. */
-    printMsg(lvlChatty, "executing builder '%1%'", drv->builder);
-
-    /* Create the log file. */
-    Path logFile = openLogFile();
-
-    /* Create a pipe to get the output of the builder. */
-    //builderOut.create();
-
-    builderOut.readSide = posix_openpt(O_RDWR | O_NOCTTY);
-    if (!builderOut.readSide)
-        throw SysError("opening pseudoterminal master");
-
-    std::string slaveName(ptsname(builderOut.readSide.get()));
-
-    if (buildUser) {
-        if (chmod(slaveName.c_str(), 0600))
-            throw SysError("changing mode of pseudoterminal slave");
-
-        if (chown(slaveName.c_str(), buildUser->getUID(), 0))
-            throw SysError("changing owner of pseudoterminal slave");
-    }
-#if __APPLE__
-    else {
-        if (grantpt(builderOut.readSide.get()))
-            throw SysError("granting access to pseudoterminal slave");
-    }
-#endif
-
-    #if 0
-    // Mount the pt in the sandbox so that the "tty" command works.
-    // FIXME: this doesn't work with the new devpts in the sandbox.
-    if (useChroot)
-        dirsInChroot[slaveName] = {slaveName, false};
-    #endif
-
-    if (unlockpt(builderOut.readSide.get()))
-        throw SysError("unlocking pseudoterminal");
-
-    builderOut.writeSide = open(slaveName.c_str(), O_RDWR | O_NOCTTY);
-    if (!builderOut.writeSide)
-        throw SysError("opening pseudoterminal slave");
-
-    // Put the pt into raw mode to prevent \n -> \r\n translation.
-    struct termios term;
-    if (tcgetattr(builderOut.writeSide.get(), &term))
-        throw SysError("getting pseudoterminal attributes");
-
-    cfmakeraw(&term);
-
-    if (tcsetattr(builderOut.writeSide.get(), TCSANOW, &term))
-        throw SysError("putting pseudoterminal into raw mode");
-
-    result.startTime = time(0);
-
-    /* Fork a child to build the package. */
-    ProcessOptions options;
-
-#if __linux__
-    if (useChroot) {
-        /* Set up private namespaces for the build:
-
-           - The PID namespace causes the build to start as PID 1.
-             Processes outside of the chroot are not visible to those
-             on the inside, but processes inside the chroot are
-             visible from the outside (though with different PIDs).
-
-           - The private mount namespace ensures that all the bind
-             mounts we do will only show up in this process and its
-             children, and will disappear automatically when we're
-             done.
-
-           - The private network namespace ensures that the builder
-             cannot talk to the outside world (or vice versa).  It
-             only has a private loopback interface. (Fixed-output
-             derivations are not run in a private network namespace
-             to allow functions like fetchurl to work.)
-
-           - The IPC namespace prevents the builder from communicating
-             with outside processes using SysV IPC mechanisms (shared
-             memory, message queues, semaphores).  It also ensures
-             that all IPC objects are destroyed when the builder
-             exits.
-
-           - The UTS namespace ensures that builders see a hostname of
-             localhost rather than the actual hostname.
-
-           We use a helper process to do the clone() to work around
-           clone() being broken in multi-threaded programs due to
-           at-fork handlers not being run. Note that we use
-           CLONE_PARENT to ensure that the real builder is parented to
-           us.
-        */
-
-        if (!(derivationIsImpure(derivationType)))
-            privateNetwork = true;
-
-        userNamespaceSync.create();
-
-        options.allowVfork = false;
-
-        Path maxUserNamespaces = "/proc/sys/user/max_user_namespaces";
-        static bool userNamespacesEnabled =
-            pathExists(maxUserNamespaces)
-            && trim(readFile(maxUserNamespaces)) != "0";
-
-        usingUserNamespace = userNamespacesEnabled;
-
-        Pid helper = startProcess([&]() {
-
-            /* Drop additional groups here because we can't do it
-               after we've created the new user namespace.  FIXME:
-               this means that if we're not root in the parent
-               namespace, we can't drop additional groups; they will
-               be mapped to nogroup in the child namespace. There does
-               not seem to be a workaround for this. (But who can tell
-               from reading user_namespaces(7)?)
-               See also https://lwn.net/Articles/621612/. */
-            if (getuid() == 0 && setgroups(0, 0) == -1)
-                throw SysError("setgroups failed");
-
-            size_t stackSize = 1 * 1024 * 1024;
-            char * stack = (char *) mmap(0, stackSize,
-                PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
-            if (stack == MAP_FAILED) throw SysError("allocating stack");
-
-            int flags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_PARENT | SIGCHLD;
-            if (privateNetwork)
-                flags |= CLONE_NEWNET;
-            if (usingUserNamespace)
-                flags |= CLONE_NEWUSER;
-
-            pid_t child = clone(childEntry, stack + stackSize, flags, this);
-            if (child == -1 && errno == EINVAL) {
-                /* Fallback for Linux < 2.13 where CLONE_NEWPID and
-                   CLONE_PARENT are not allowed together. */
-                flags &= ~CLONE_NEWPID;
-                child = clone(childEntry, stack + stackSize, flags, this);
-            }
-            if (usingUserNamespace && child == -1 && (errno == EPERM || errno == EINVAL)) {
-                /* Some distros patch Linux to not allow unprivileged
-                 * user namespaces. If we get EPERM or EINVAL, try
-                 * without CLONE_NEWUSER and see if that works.
-                 */
-                usingUserNamespace = false;
-                flags &= ~CLONE_NEWUSER;
-                child = clone(childEntry, stack + stackSize, flags, this);
-            }
-            /* Otherwise exit with EPERM so we can handle this in the
-               parent. This is only done when sandbox-fallback is set
-               to true (the default). */
-            if (child == -1 && (errno == EPERM || errno == EINVAL) && settings.sandboxFallback)
-                _exit(1);
-            if (child == -1) throw SysError("cloning builder process");
-
-            writeFull(builderOut.writeSide.get(),
-                fmt("%d %d\n", usingUserNamespace, child));
-            _exit(0);
-        }, options);
-
-        int res = helper.wait();
-        if (res != 0 && settings.sandboxFallback) {
-            useChroot = false;
-            initTmpDir();
-            goto fallback;
-        } else if (res != 0)
-            throw Error("unable to start build process");
-
-        userNamespaceSync.readSide = -1;
-
-        /* Close the write side to prevent runChild() from hanging
-           reading from this. */
-        Finally cleanup([&]() {
-            userNamespaceSync.writeSide = -1;
-        });
-
-        auto ss = tokenizeString<std::vector<std::string>>(readLine(builderOut.readSide.get()));
-        assert(ss.size() == 2);
-        usingUserNamespace = ss[0] == "1";
-        pid = string2Int<pid_t>(ss[1]).value();
-
-        if (usingUserNamespace) {
-            /* Set the UID/GID mapping of the builder's user namespace
-               such that the sandbox user maps to the build user, or to
-               the calling user (if build users are disabled). */
-            uid_t hostUid = buildUser ? buildUser->getUID() : getuid();
-            uid_t hostGid = buildUser ? buildUser->getGID() : getgid();
-
-            writeFile("/proc/" + std::to_string(pid) + "/uid_map",
-                fmt("%d %d 1", sandboxUid(), hostUid));
-
-            writeFile("/proc/" + std::to_string(pid) + "/setgroups", "deny");
-
-            writeFile("/proc/" + std::to_string(pid) + "/gid_map",
-                fmt("%d %d 1", sandboxGid(), hostGid));
-        } else {
-            debug("note: not using a user namespace");
-            if (!buildUser)
-                throw Error("cannot perform a sandboxed build because user namespaces are not enabled; check /proc/sys/user/max_user_namespaces");
-        }
-
-        /* Now that we now the sandbox uid, we can write
-           /etc/passwd. */
-        writeFile(chrootRootDir + "/etc/passwd", fmt(
-                "root:x:0:0:Nix build user:%3%:/noshell\n"
-                "nixbld:x:%1%:%2%:Nix build user:%3%:/noshell\n"
-                "nobody:x:65534:65534:Nobody:/:/noshell\n",
-                sandboxUid(), sandboxGid(), settings.sandboxBuildDir));
-
-        /* Save the mount namespace of the child. We have to do this
-           *before* the child does a chroot. */
-        sandboxMountNamespace = open(fmt("/proc/%d/ns/mnt", (pid_t) pid).c_str(), O_RDONLY);
-        if (sandboxMountNamespace.get() == -1)
-            throw SysError("getting sandbox mount namespace");
-
-        /* Signal the builder that we've updated its user namespace. */
-        writeFull(userNamespaceSync.writeSide.get(), "1");
-
-    } else
-#endif
-    {
-    fallback:
-        options.allowVfork = !buildUser && !drv->isBuiltin();
-        pid = startProcess([&]() {
-            runChild();
-        }, options);
-    }
-
-    /* parent */
-    pid.setSeparatePG(true);
-    builderOut.writeSide = -1;
-    worker.childStarted(shared_from_this(), {builderOut.readSide.get()}, true, true);
-
-    /* Check if setting up the build environment failed. */
-    std::vector<std::string> msgs;
-    while (true) {
-        string msg = [&]() {
-            try {
-                return readLine(builderOut.readSide.get());
-            } catch (Error & e) {
-                e.addTrace({}, "while waiting for the build environment to initialize (previous messages: %s)",
-                    concatStringsSep("|", msgs));
-                throw e;
-            }
-        }();
-        if (string(msg, 0, 1) == "\2") break;
-        if (string(msg, 0, 1) == "\1") {
-            FdSource source(builderOut.readSide.get());
-            auto ex = readError(source);
-            ex.addTrace({}, "while setting up the build environment");
-            throw ex;
-        }
-        debug("sandbox setup: " + msg);
-        msgs.push_back(std::move(msg));
-    }
-}
-
-
-void DerivationGoal::initTmpDir() {
-    /* In a sandbox, for determinism, always use the same temporary
-       directory. */
-#if __linux__
-    tmpDirInSandbox = useChroot ? settings.sandboxBuildDir : tmpDir;
-#else
-    tmpDirInSandbox = tmpDir;
-#endif
-
-    /* In non-structured mode, add all bindings specified in the
-       derivation via the environment, except those listed in the
-       passAsFile attribute. Those are passed as file names pointing
-       to temporary files containing the contents. Note that
-       passAsFile is ignored in structure mode because it's not
-       needed (attributes are not passed through the environment, so
-       there is no size constraint). */
-    if (!parsedDrv->getStructuredAttrs()) {
-
-        StringSet passAsFile = tokenizeString<StringSet>(get(drv->env, "passAsFile").value_or(""));
-        for (auto & i : drv->env) {
-            if (passAsFile.find(i.first) == passAsFile.end()) {
-                env[i.first] = i.second;
-            } else {
-                auto hash = hashString(htSHA256, i.first);
-                string fn = ".attr-" + hash.to_string(Base32, false);
-                Path p = tmpDir + "/" + fn;
-                writeFile(p, rewriteStrings(i.second, inputRewrites));
-                chownToBuilder(p);
-                env[i.first + "Path"] = tmpDirInSandbox + "/" + fn;
-            }
-        }
-
-    }
-
-    /* For convenience, set an environment pointing to the top build
-       directory. */
-    env["NIX_BUILD_TOP"] = tmpDirInSandbox;
-
-    /* Also set TMPDIR and variants to point to this directory. */
-    env["TMPDIR"] = env["TEMPDIR"] = env["TMP"] = env["TEMP"] = tmpDirInSandbox;
-
-    /* Explicitly set PWD to prevent problems with chroot builds.  In
-       particular, dietlibc cannot figure out the cwd because the
-       inode of the current directory doesn't appear in .. (because
-       getdents returns the inode of the mount point). */
-    env["PWD"] = tmpDirInSandbox;
-}
-
-
-void DerivationGoal::initEnv()
-{
-    env.clear();
-
-    /* Most shells initialise PATH to some default (/bin:/usr/bin:...) when
-       PATH is not set.  We don't want this, so we fill it in with some dummy
-       value. */
-    env["PATH"] = "/path-not-set";
-
-    /* Set HOME to a non-existing path to prevent certain programs from using
-       /etc/passwd (or NIS, or whatever) to locate the home directory (for
-       example, wget looks for ~/.wgetrc).  I.e., these tools use /etc/passwd
-       if HOME is not set, but they will just assume that the settings file
-       they are looking for does not exist if HOME is set but points to some
-       non-existing path. */
-    env["HOME"] = homeDir;
-
-    /* Tell the builder where the Nix store is.  Usually they
-       shouldn't care, but this is useful for purity checking (e.g.,
-       the compiler or linker might only want to accept paths to files
-       in the store or in the build directory). */
-    env["NIX_STORE"] = worker.store.storeDir;
-
-    /* The maximum number of cores to utilize for parallel building. */
-    env["NIX_BUILD_CORES"] = (format("%d") % settings.buildCores).str();
-
-    initTmpDir();
-
-    /* Compatibility hack with Nix <= 0.7: if this is a fixed-output
-       derivation, tell the builder, so that for instance `fetchurl'
-       can skip checking the output.  On older Nixes, this environment
-       variable won't be set, so `fetchurl' will do the check. */
-    if (derivationIsFixed(derivationType)) env["NIX_OUTPUT_CHECKED"] = "1";
-
-    /* *Only* if this is a fixed-output derivation, propagate the
-       values of the environment variables specified in the
-       `impureEnvVars' attribute to the builder.  This allows for
-       instance environment variables for proxy configuration such as
-       `http_proxy' to be easily passed to downloaders like
-       `fetchurl'.  Passing such environment variables from the caller
-       to the builder is generally impure, but the output of
-       fixed-output derivations is by definition pure (since we
-       already know the cryptographic hash of the output). */
-    if (derivationIsImpure(derivationType)) {
-        for (auto & i : parsedDrv->getStringsAttr("impureEnvVars").value_or(Strings()))
-            env[i] = getEnv(i).value_or("");
-    }
-
-    /* Currently structured log messages piggyback on stderr, but we
-       may change that in the future. So tell the builder which file
-       descriptor to use for that. */
-    env["NIX_LOG_FD"] = "2";
-
-    /* Trigger colored output in various tools. */
-    env["TERM"] = "xterm-256color";
-}
-
-
-static std::regex shVarName("[A-Za-z_][A-Za-z0-9_]*");
-
-
-void DerivationGoal::writeStructuredAttrs()
-{
-    auto structuredAttrs = parsedDrv->getStructuredAttrs();
-    if (!structuredAttrs) return;
-
-    auto json = *structuredAttrs;
-
-    /* Add an "outputs" object containing the output paths. */
-    nlohmann::json outputs;
-    for (auto & i : drv->outputs) {
-        /* The placeholder must have a rewrite, so we use it to cover both the
-           cases where we know or don't know the output path ahead of time. */
-        outputs[i.first] = rewriteStrings(hashPlaceholder(i.first), inputRewrites);
-    }
-    json["outputs"] = outputs;
-
-    /* Handle exportReferencesGraph. */
-    auto e = json.find("exportReferencesGraph");
-    if (e != json.end() && e->is_object()) {
-        for (auto i = e->begin(); i != e->end(); ++i) {
-            std::ostringstream str;
-            {
-                JSONPlaceholder jsonRoot(str, true);
-                StorePathSet storePaths;
-                for (auto & p : *i)
-                    storePaths.insert(worker.store.parseStorePath(p.get<std::string>()));
-                worker.store.pathInfoToJSON(jsonRoot,
-                    exportReferences(storePaths), false, true);
-            }
-            json[i.key()] = nlohmann::json::parse(str.str()); // urgh
-        }
-    }
-
-    writeFile(tmpDir + "/.attrs.json", rewriteStrings(json.dump(), inputRewrites));
-    chownToBuilder(tmpDir + "/.attrs.json");
-
-    /* As a convenience to bash scripts, write a shell file that
-       maps all attributes that are representable in bash -
-       namely, strings, integers, nulls, Booleans, and arrays and
-       objects consisting entirely of those values. (So nested
-       arrays or objects are not supported.) */
-
-    auto handleSimpleType = [](const nlohmann::json & value) -> std::optional<std::string> {
-        if (value.is_string())
-            return shellEscape(value);
-
-        if (value.is_number()) {
-            auto f = value.get<float>();
-            if (std::ceil(f) == f)
-                return std::to_string(value.get<int>());
-        }
-
-        if (value.is_null())
-            return std::string("''");
-
-        if (value.is_boolean())
-            return value.get<bool>() ? std::string("1") : std::string("");
-
-        return {};
-    };
-
-    std::string jsonSh;
-
-    for (auto i = json.begin(); i != json.end(); ++i) {
-
-        if (!std::regex_match(i.key(), shVarName)) continue;
-
-        auto & value = i.value();
-
-        auto s = handleSimpleType(value);
-        if (s)
-            jsonSh += fmt("declare %s=%s\n", i.key(), *s);
-
-        else if (value.is_array()) {
-            std::string s2;
-            bool good = true;
-
-            for (auto i = value.begin(); i != value.end(); ++i) {
-                auto s3 = handleSimpleType(i.value());
-                if (!s3) { good = false; break; }
-                s2 += *s3; s2 += ' ';
-            }
-
-            if (good)
-                jsonSh += fmt("declare -a %s=(%s)\n", i.key(), s2);
-        }
-
-        else if (value.is_object()) {
-            std::string s2;
-            bool good = true;
-
-            for (auto i = value.begin(); i != value.end(); ++i) {
-                auto s3 = handleSimpleType(i.value());
-                if (!s3) { good = false; break; }
-                s2 += fmt("[%s]=%s ", shellEscape(i.key()), *s3);
-            }
-
-            if (good)
-                jsonSh += fmt("declare -A %s=(%s)\n", i.key(), s2);
-        }
-    }
-
-    writeFile(tmpDir + "/.attrs.sh", rewriteStrings(jsonSh, inputRewrites));
-    chownToBuilder(tmpDir + "/.attrs.sh");
-}
-
-struct RestrictedStoreConfig : virtual LocalFSStoreConfig
-{
-    using LocalFSStoreConfig::LocalFSStoreConfig;
-    const std::string name() { return "Restricted Store"; }
-};
-
-/* A wrapper around LocalStore that only allows building/querying of
-   paths that are in the input closures of the build or were added via
-   recursive Nix calls. */
-struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual LocalFSStore
-{
-    ref<LocalStore> next;
-
-    DerivationGoal & goal;
-
-    RestrictedStore(const Params & params, ref<LocalStore> next, DerivationGoal & goal)
-        : StoreConfig(params)
-        , LocalFSStoreConfig(params)
-        , RestrictedStoreConfig(params)
-        , Store(params)
-        , LocalFSStore(params)
-        , next(next), goal(goal)
-    { }
-
-    Path getRealStoreDir() override
-    { return next->realStoreDir; }
-
-    std::string getUri() override
-    { return next->getUri(); }
-
-    StorePathSet queryAllValidPaths() override
-    {
-        StorePathSet paths;
-        for (auto & p : goal.inputPaths) paths.insert(p);
-        for (auto & p : goal.addedPaths) paths.insert(p);
-        return paths;
-    }
-
-    void queryPathInfoUncached(const StorePath & path,
-        Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept override
-    {
-        if (goal.isAllowed(path)) {
-            try {
-                /* Censor impure information. */
-                auto info = std::make_shared<ValidPathInfo>(*next->queryPathInfo(path));
-                info->deriver.reset();
-                info->registrationTime = 0;
-                info->ultimate = false;
-                info->sigs.clear();
-                callback(info);
-            } catch (InvalidPath &) {
-                callback(nullptr);
-            }
-        } else
-            callback(nullptr);
-    };
-
-    void queryReferrers(const StorePath & path, StorePathSet & referrers) override
-    { }
-
-    std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(const StorePath & path) override
-    {
-        if (!goal.isAllowed(path))
-            throw InvalidPath("cannot query output map for unknown path '%s' in recursive Nix", printStorePath(path));
-        return next->queryPartialDerivationOutputMap(path);
-    }
-
-    std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override
-    { throw Error("queryPathFromHashPart"); }
-
-    StorePath addToStore(const string & name, const Path & srcPath,
-        FileIngestionMethod method = FileIngestionMethod::Recursive, HashType hashAlgo = htSHA256,
-        PathFilter & filter = defaultPathFilter, RepairFlag repair = NoRepair) override
-    { throw Error("addToStore"); }
-
-    void addToStore(const ValidPathInfo & info, Source & narSource,
-        RepairFlag repair = NoRepair, CheckSigsFlag checkSigs = CheckSigs) override
-    {
-        next->addToStore(info, narSource, repair, checkSigs);
-        goal.addDependency(info.path);
-    }
-
-    StorePath addTextToStore(const string & name, const string & s,
-        const StorePathSet & references, RepairFlag repair = NoRepair) override
-    {
-        auto path = next->addTextToStore(name, s, references, repair);
-        goal.addDependency(path);
-        return path;
-    }
-
-    StorePath addToStoreFromDump(Source & dump, const string & name,
-        FileIngestionMethod method = FileIngestionMethod::Recursive, HashType hashAlgo = htSHA256, RepairFlag repair = NoRepair) override
-    {
-        auto path = next->addToStoreFromDump(dump, name, method, hashAlgo, repair);
-        goal.addDependency(path);
-        return path;
-    }
-
-    void narFromPath(const StorePath & path, Sink & sink) override
-    {
-        if (!goal.isAllowed(path))
-            throw InvalidPath("cannot dump unknown path '%s' in recursive Nix", printStorePath(path));
-        LocalFSStore::narFromPath(path, sink);
-    }
-
-    void ensurePath(const StorePath & path) override
-    {
-        if (!goal.isAllowed(path))
-            throw InvalidPath("cannot substitute unknown path '%s' in recursive Nix", printStorePath(path));
-        /* Nothing to be done; 'path' must already be valid. */
-    }
-
-    void registerDrvOutput(const Realisation & info) override
-    // XXX: This should probably be allowed as a no-op if the realisation
-    // corresponds to an allowed derivation
-    { throw Error("registerDrvOutput"); }
-
-    std::optional<const Realisation> queryRealisation(const DrvOutput & id) override
-    // XXX: This should probably be allowed if the realisation corresponds to
-    // an allowed derivation
-    { throw Error("queryRealisation"); }
-
-    void buildPaths(const std::vector<StorePathWithOutputs> & paths, BuildMode buildMode) override
-    {
-        if (buildMode != bmNormal) throw Error("unsupported build mode");
-
-        StorePathSet newPaths;
-
-        for (auto & path : paths) {
-            if (!goal.isAllowed(path.path))
-                throw InvalidPath("cannot build unknown path '%s' in recursive Nix", printStorePath(path.path));
-        }
-
-        next->buildPaths(paths, buildMode);
-
-        for (auto & path : paths) {
-            if (!path.path.isDerivation()) continue;
-            auto outputs = next->queryDerivationOutputMap(path.path);
-            for (auto & output : outputs)
-                if (wantOutput(output.first, path.outputs))
-                    newPaths.insert(output.second);
-        }
-
-        StorePathSet closure;
-        next->computeFSClosure(newPaths, closure);
-        for (auto & path : closure)
-            goal.addDependency(path);
-    }
-
-    BuildResult buildDerivation(const StorePath & drvPath, const BasicDerivation & drv,
-        BuildMode buildMode = bmNormal) override
-    { unsupported("buildDerivation"); }
-
-    void addTempRoot(const StorePath & path) override
-    { }
-
-    void addIndirectRoot(const Path & path) override
-    { }
-
-    Roots findRoots(bool censor) override
-    { return Roots(); }
-
-    void collectGarbage(const GCOptions & options, GCResults & results) override
-    { }
-
-    void addSignatures(const StorePath & storePath, const StringSet & sigs) override
-    { unsupported("addSignatures"); }
-
-    void queryMissing(const std::vector<StorePathWithOutputs> & targets,
-        StorePathSet & willBuild, StorePathSet & willSubstitute, StorePathSet & unknown,
-        uint64_t & downloadSize, uint64_t & narSize) override
-    {
-        /* This is slightly impure since it leaks information to the
-           client about what paths will be built/substituted or are
-           already present. Probably not a big deal. */
-
-        std::vector<StorePathWithOutputs> allowed;
-        for (auto & path : targets) {
-            if (goal.isAllowed(path.path))
-                allowed.emplace_back(path);
-            else
-                unknown.insert(path.path);
-        }
-
-        next->queryMissing(allowed, willBuild, willSubstitute,
-            unknown, downloadSize, narSize);
-    }
-};
-
-
-void DerivationGoal::startDaemon()
-{
-    settings.requireExperimentalFeature("recursive-nix");
-
-    Store::Params params;
-    params["path-info-cache-size"] = "0";
-    params["store"] = worker.store.storeDir;
-    if (auto localStore = dynamic_cast<LocalStore *>(&worker.store))
-        params["root"] = localStore->rootDir;
-    params["state"] = "/no-such-path";
-    params["log"] = "/no-such-path";
-    auto store = make_ref<RestrictedStore>(params,
-        ref<LocalStore>(std::dynamic_pointer_cast<LocalStore>(worker.store.shared_from_this())),
-        *this);
-
-    addedPaths.clear();
-
-    auto socketName = ".nix-socket";
-    Path socketPath = tmpDir + "/" + socketName;
-    env["NIX_REMOTE"] = "unix://" + tmpDirInSandbox + "/" + socketName;
-
-    daemonSocket = createUnixDomainSocket(socketPath, 0600);
-
-    chownToBuilder(socketPath);
-
-    daemonThread = std::thread([this, store]() {
-
-        while (true) {
-
-            /* Accept a connection. */
-            struct sockaddr_un remoteAddr;
-            socklen_t remoteAddrLen = sizeof(remoteAddr);
-
-            AutoCloseFD remote = accept(daemonSocket.get(),
-                (struct sockaddr *) &remoteAddr, &remoteAddrLen);
-            if (!remote) {
-                if (errno == EINTR) continue;
-                if (errno == EINVAL) break;
-                throw SysError("accepting connection");
-            }
-
-            closeOnExec(remote.get());
-
-            debug("received daemon connection");
-
-            auto workerThread = std::thread([store, remote{std::move(remote)}]() {
-                FdSource from(remote.get());
-                FdSink to(remote.get());
-                try {
-                    daemon::processConnection(store, from, to,
-                        daemon::NotTrusted, daemon::Recursive,
-                        [&](Store & store) { store.createUser("nobody", 65535); });
-                    debug("terminated daemon connection");
-                } catch (SysError &) {
-                    ignoreException();
-                }
-            });
-
-            daemonWorkerThreads.push_back(std::move(workerThread));
-        }
-
-        debug("daemon shutting down");
-    });
-}
-
-
-void DerivationGoal::stopDaemon()
-{
-    if (daemonSocket && shutdown(daemonSocket.get(), SHUT_RDWR) == -1)
-        throw SysError("shutting down daemon socket");
-
-    if (daemonThread.joinable())
-        daemonThread.join();
-
-    // FIXME: should prune worker threads more quickly.
-    // FIXME: shutdown the client socket to speed up worker termination.
-    for (auto & thread : daemonWorkerThreads)
-        thread.join();
-    daemonWorkerThreads.clear();
-
-    daemonSocket = -1;
-}
-
-
-void DerivationGoal::addDependency(const StorePath & path)
-{
-    if (isAllowed(path)) return;
-
-    addedPaths.insert(path);
-
-    /* If we're doing a sandbox build, then we have to make the path
-       appear in the sandbox. */
-    if (useChroot) {
-
-        debug("materialising '%s' in the sandbox", worker.store.printStorePath(path));
-
-        #if __linux__
-
-            Path source = worker.store.Store::toRealPath(path);
-            Path target = chrootRootDir + worker.store.printStorePath(path);
-            debug("bind-mounting %s -> %s", target, source);
-
-            if (pathExists(target))
-                throw Error("store path '%s' already exists in the sandbox", worker.store.printStorePath(path));
-
-            auto st = lstat(source);
-
-            if (S_ISDIR(st.st_mode)) {
-
-                /* Bind-mount the path into the sandbox. This requires
-                   entering its mount namespace, which is not possible
-                   in multithreaded programs. So we do this in a
-                   child process.*/
-                Pid child(startProcess([&]() {
-
-                    if (setns(sandboxMountNamespace.get(), 0) == -1)
-                        throw SysError("entering sandbox mount namespace");
-
-                    createDirs(target);
-
-                    if (mount(source.c_str(), target.c_str(), "", MS_BIND, 0) == -1)
-                        throw SysError("bind mount from '%s' to '%s' failed", source, target);
-
-                    _exit(0);
-                }));
-
-                int status = child.wait();
-                if (status != 0)
-                    throw Error("could not add path '%s' to sandbox", worker.store.printStorePath(path));
-
-            } else
-                linkOrCopy(source, target);
-
-        #else
-            throw Error("don't know how to make path '%s' (produced by a recursive Nix call) appear in the sandbox",
-                worker.store.printStorePath(path));
-        #endif
-
-    }
-}
-
-
-void DerivationGoal::chownToBuilder(const Path & path)
-{
-    if (!buildUser) return;
-    if (chown(path.c_str(), buildUser->getUID(), buildUser->getGID()) == -1)
-        throw SysError("cannot change ownership of '%1%'", path);
-}
-
-
-void setupSeccomp()
-{
-#if __linux__
-    if (!settings.filterSyscalls) return;
-#if HAVE_SECCOMP
-    scmp_filter_ctx ctx;
-
-    if (!(ctx = seccomp_init(SCMP_ACT_ALLOW)))
-        throw SysError("unable to initialize seccomp mode 2");
-
-    Finally cleanup([&]() {
-        seccomp_release(ctx);
-    });
-
-    if (nativeSystem == "x86_64-linux" &&
-        seccomp_arch_add(ctx, SCMP_ARCH_X86) != 0)
-        throw SysError("unable to add 32-bit seccomp architecture");
-
-    if (nativeSystem == "x86_64-linux" &&
-        seccomp_arch_add(ctx, SCMP_ARCH_X32) != 0)
-        throw SysError("unable to add X32 seccomp architecture");
-
-    if (nativeSystem == "aarch64-linux" &&
-        seccomp_arch_add(ctx, SCMP_ARCH_ARM) != 0)
-        printError("unable to add ARM seccomp architecture; this may result in spurious build failures if running 32-bit ARM processes");
-
-    /* Prevent builders from creating setuid/setgid binaries. */
-    for (int perm : { S_ISUID, S_ISGID }) {
-        if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(chmod), 1,
-                SCMP_A1(SCMP_CMP_MASKED_EQ, (scmp_datum_t) perm, (scmp_datum_t) perm)) != 0)
-            throw SysError("unable to add seccomp rule");
-
-        if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(fchmod), 1,
-                SCMP_A1(SCMP_CMP_MASKED_EQ, (scmp_datum_t) perm, (scmp_datum_t) perm)) != 0)
-            throw SysError("unable to add seccomp rule");
-
-        if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(fchmodat), 1,
-                SCMP_A2(SCMP_CMP_MASKED_EQ, (scmp_datum_t) perm, (scmp_datum_t) perm)) != 0)
-            throw SysError("unable to add seccomp rule");
-    }
-
-    /* Prevent builders from creating EAs or ACLs. Not all filesystems
-       support these, and they're not allowed in the Nix store because
-       they're not representable in the NAR serialisation. */
-    if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ENOTSUP), SCMP_SYS(setxattr), 0) != 0 ||
-        seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ENOTSUP), SCMP_SYS(lsetxattr), 0) != 0 ||
-        seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ENOTSUP), SCMP_SYS(fsetxattr), 0) != 0)
-        throw SysError("unable to add seccomp rule");
-
-    if (seccomp_attr_set(ctx, SCMP_FLTATR_CTL_NNP, settings.allowNewPrivileges ? 0 : 1) != 0)
-        throw SysError("unable to set 'no new privileges' seccomp attribute");
-
-    if (seccomp_load(ctx) != 0)
-        throw SysError("unable to load seccomp BPF program");
-#else
-    throw Error(
-        "seccomp is not supported on this platform; "
-        "you can bypass this error by setting the option 'filter-syscalls' to false, but note that untrusted builds can then create setuid binaries!");
-#endif
-#endif
-}
-
-
-void DerivationGoal::runChild()
-{
-    /* Warning: in the child we should absolutely not make any SQLite
-       calls! */
-
-    try { /* child */
-
-        commonChildInit(builderOut);
-
-        try {
-            setupSeccomp();
-        } catch (...) {
-            if (buildUser) throw;
-        }
-
-        bool setUser = true;
-
-        /* Make the contents of netrc available to builtin:fetchurl
-           (which may run under a different uid and/or in a sandbox). */
-        std::string netrcData;
-        try {
-            if (drv->isBuiltin() && drv->builder == "builtin:fetchurl")
-                netrcData = readFile(settings.netrcFile);
-        } catch (SysError &) { }
-
-#if __linux__
-        if (useChroot) {
-
-            userNamespaceSync.writeSide = -1;
-
-            if (drainFD(userNamespaceSync.readSide.get()) != "1")
-                throw Error("user namespace initialisation failed");
-
-            userNamespaceSync.readSide = -1;
-
-            if (privateNetwork) {
-
-                /* Initialise the loopback interface. */
-                AutoCloseFD fd(socket(PF_INET, SOCK_DGRAM, IPPROTO_IP));
-                if (!fd) throw SysError("cannot open IP socket");
-
-                struct ifreq ifr;
-                strcpy(ifr.ifr_name, "lo");
-                ifr.ifr_flags = IFF_UP | IFF_LOOPBACK | IFF_RUNNING;
-                if (ioctl(fd.get(), SIOCSIFFLAGS, &ifr) == -1)
-                    throw SysError("cannot set loopback interface flags");
-            }
-
-            /* Set the hostname etc. to fixed values. */
-            char hostname[] = "localhost";
-            if (sethostname(hostname, sizeof(hostname)) == -1)
-                throw SysError("cannot set host name");
-            char domainname[] = "(none)"; // kernel default
-            if (setdomainname(domainname, sizeof(domainname)) == -1)
-                throw SysError("cannot set domain name");
-
-            /* Make all filesystems private.  This is necessary
-               because subtrees may have been mounted as "shared"
-               (MS_SHARED).  (Systemd does this, for instance.)  Even
-               though we have a private mount namespace, mounting
-               filesystems on top of a shared subtree still propagates
-               outside of the namespace.  Making a subtree private is
-               local to the namespace, though, so setting MS_PRIVATE
-               does not affect the outside world. */
-            if (mount(0, "/", 0, MS_PRIVATE | MS_REC, 0) == -1)
-                throw SysError("unable to make '/' private");
-
-            /* Bind-mount chroot directory to itself, to treat it as a
-               different filesystem from /, as needed for pivot_root. */
-            if (mount(chrootRootDir.c_str(), chrootRootDir.c_str(), 0, MS_BIND, 0) == -1)
-                throw SysError("unable to bind mount '%1%'", chrootRootDir);
-
-            /* Bind-mount the sandbox's Nix store onto itself so that
-               we can mark it as a "shared" subtree, allowing bind
-               mounts made in *this* mount namespace to be propagated
-               into the child namespace created by the
-               unshare(CLONE_NEWNS) call below.
-
-               Marking chrootRootDir as MS_SHARED causes pivot_root()
-               to fail with EINVAL. Don't know why. */
-            Path chrootStoreDir = chrootRootDir + worker.store.storeDir;
-
-            if (mount(chrootStoreDir.c_str(), chrootStoreDir.c_str(), 0, MS_BIND, 0) == -1)
-                throw SysError("unable to bind mount the Nix store", chrootStoreDir);
-
-            if (mount(0, chrootStoreDir.c_str(), 0, MS_SHARED, 0) == -1)
-                throw SysError("unable to make '%s' shared", chrootStoreDir);
-
-            /* Set up a nearly empty /dev, unless the user asked to
-               bind-mount the host /dev. */
-            Strings ss;
-            if (dirsInChroot.find("/dev") == dirsInChroot.end()) {
-                createDirs(chrootRootDir + "/dev/shm");
-                createDirs(chrootRootDir + "/dev/pts");
-                ss.push_back("/dev/full");
-                if (worker.store.systemFeatures.get().count("kvm") && pathExists("/dev/kvm"))
-                    ss.push_back("/dev/kvm");
-                ss.push_back("/dev/null");
-                ss.push_back("/dev/random");
-                ss.push_back("/dev/tty");
-                ss.push_back("/dev/urandom");
-                ss.push_back("/dev/zero");
-                createSymlink("/proc/self/fd", chrootRootDir + "/dev/fd");
-                createSymlink("/proc/self/fd/0", chrootRootDir + "/dev/stdin");
-                createSymlink("/proc/self/fd/1", chrootRootDir + "/dev/stdout");
-                createSymlink("/proc/self/fd/2", chrootRootDir + "/dev/stderr");
-            }
-
-            /* Fixed-output derivations typically need to access the
-               network, so give them access to /etc/resolv.conf and so
-               on. */
-            if (derivationIsImpure(derivationType)) {
-                ss.push_back("/etc/resolv.conf");
-
-                // Only use nss functions to resolve hosts and
-                // services. Don’t use it for anything else that may
-                // be configured for this system. This limits the
-                // potential impurities introduced in fixed-outputs.
-                writeFile(chrootRootDir + "/etc/nsswitch.conf", "hosts: files dns\nservices: files\n");
-
-                ss.push_back("/etc/services");
-                ss.push_back("/etc/hosts");
-                if (pathExists("/var/run/nscd/socket"))
-                    ss.push_back("/var/run/nscd/socket");
-            }
-
-            for (auto & i : ss) dirsInChroot.emplace(i, i);
-
-            /* Bind-mount all the directories from the "host"
-               filesystem that we want in the chroot
-               environment. */
-            auto doBind = [&](const Path & source, const Path & target, bool optional = false) {
-                debug("bind mounting '%1%' to '%2%'", source, target);
-                struct stat st;
-                if (stat(source.c_str(), &st) == -1) {
-                    if (optional && errno == ENOENT)
-                        return;
-                    else
-                        throw SysError("getting attributes of path '%1%'", source);
-                }
-                if (S_ISDIR(st.st_mode))
-                    createDirs(target);
-                else {
-                    createDirs(dirOf(target));
-                    writeFile(target, "");
-                }
-                if (mount(source.c_str(), target.c_str(), "", MS_BIND | MS_REC, 0) == -1)
-                    throw SysError("bind mount from '%1%' to '%2%' failed", source, target);
-            };
-
-            for (auto & i : dirsInChroot) {
-                if (i.second.source == "/proc") continue; // backwards compatibility
-                doBind(i.second.source, chrootRootDir + i.first, i.second.optional);
-            }
-
-            /* Bind a new instance of procfs on /proc. */
-            createDirs(chrootRootDir + "/proc");
-            if (mount("none", (chrootRootDir + "/proc").c_str(), "proc", 0, 0) == -1)
-                throw SysError("mounting /proc");
-
-            /* Mount a new tmpfs on /dev/shm to ensure that whatever
-               the builder puts in /dev/shm is cleaned up automatically. */
-            if (pathExists("/dev/shm") && mount("none", (chrootRootDir + "/dev/shm").c_str(), "tmpfs", 0,
-                    fmt("size=%s", settings.sandboxShmSize).c_str()) == -1)
-                throw SysError("mounting /dev/shm");
-
-            /* Mount a new devpts on /dev/pts.  Note that this
-               requires the kernel to be compiled with
-               CONFIG_DEVPTS_MULTIPLE_INSTANCES=y (which is the case
-               if /dev/ptx/ptmx exists). */
-            if (pathExists("/dev/pts/ptmx") &&
-                !pathExists(chrootRootDir + "/dev/ptmx")
-                && !dirsInChroot.count("/dev/pts"))
-            {
-                if (mount("none", (chrootRootDir + "/dev/pts").c_str(), "devpts", 0, "newinstance,mode=0620") == 0)
-                {
-                    createSymlink("/dev/pts/ptmx", chrootRootDir + "/dev/ptmx");
-
-                    /* Make sure /dev/pts/ptmx is world-writable.  With some
-                       Linux versions, it is created with permissions 0.  */
-                    chmod_(chrootRootDir + "/dev/pts/ptmx", 0666);
-                } else {
-                    if (errno != EINVAL)
-                        throw SysError("mounting /dev/pts");
-                    doBind("/dev/pts", chrootRootDir + "/dev/pts");
-                    doBind("/dev/ptmx", chrootRootDir + "/dev/ptmx");
-                }
-            }
-
-            /* Unshare this mount namespace. This is necessary because
-               pivot_root() below changes the root of the mount
-               namespace. This means that the call to setns() in
-               addDependency() would hide the host's filesystem,
-               making it impossible to bind-mount paths from the host
-               Nix store into the sandbox. Therefore, we save the
-               pre-pivot_root namespace in
-               sandboxMountNamespace. Since we made /nix/store a
-               shared subtree above, this allows addDependency() to
-               make paths appear in the sandbox. */
-            if (unshare(CLONE_NEWNS) == -1)
-                throw SysError("unsharing mount namespace");
-
-            /* Do the chroot(). */
-            if (chdir(chrootRootDir.c_str()) == -1)
-                throw SysError("cannot change directory to '%1%'", chrootRootDir);
-
-            if (mkdir("real-root", 0) == -1)
-                throw SysError("cannot create real-root directory");
-
-            if (pivot_root(".", "real-root") == -1)
-                throw SysError("cannot pivot old root directory onto '%1%'", (chrootRootDir + "/real-root"));
-
-            if (chroot(".") == -1)
-                throw SysError("cannot change root directory to '%1%'", chrootRootDir);
-
-            if (umount2("real-root", MNT_DETACH) == -1)
-                throw SysError("cannot unmount real root filesystem");
-
-            if (rmdir("real-root") == -1)
-                throw SysError("cannot remove real-root directory");
-
-            /* Switch to the sandbox uid/gid in the user namespace,
-               which corresponds to the build user or calling user in
-               the parent namespace. */
-            if (setgid(sandboxGid()) == -1)
-                throw SysError("setgid failed");
-            if (setuid(sandboxUid()) == -1)
-                throw SysError("setuid failed");
-
-            setUser = false;
-        }
-#endif
-
-        if (chdir(tmpDirInSandbox.c_str()) == -1)
-            throw SysError("changing into '%1%'", tmpDir);
-
-        /* Close all other file descriptors. */
-        closeMostFDs({STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO});
-
-#if __linux__
-        /* Change the personality to 32-bit if we're doing an
-           i686-linux build on an x86_64-linux machine. */
-        struct utsname utsbuf;
-        uname(&utsbuf);
-        if (drv->platform == "i686-linux" &&
-            (settings.thisSystem == "x86_64-linux" ||
-             (!strcmp(utsbuf.sysname, "Linux") && !strcmp(utsbuf.machine, "x86_64")))) {
-            if (personality(PER_LINUX32) == -1)
-                throw SysError("cannot set i686-linux personality");
-        }
-
-        /* Impersonate a Linux 2.6 machine to get some determinism in
-           builds that depend on the kernel version. */
-        if ((drv->platform == "i686-linux" || drv->platform == "x86_64-linux") && settings.impersonateLinux26) {
-            int cur = personality(0xffffffff);
-            if (cur != -1) personality(cur | 0x0020000 /* == UNAME26 */);
-        }
-
-        /* Disable address space randomization for improved
-           determinism. */
-        int cur = personality(0xffffffff);
-        if (cur != -1) personality(cur | ADDR_NO_RANDOMIZE);
-#endif
-
-        /* Disable core dumps by default. */
-        struct rlimit limit = { 0, RLIM_INFINITY };
-        setrlimit(RLIMIT_CORE, &limit);
-
-        // FIXME: set other limits to deterministic values?
-
-        /* Fill in the environment. */
-        Strings envStrs;
-        for (auto & i : env)
-            envStrs.push_back(rewriteStrings(i.first + "=" + i.second, inputRewrites));
-
-        /* If we are running in `build-users' mode, then switch to the
-           user we allocated above.  Make sure that we drop all root
-           privileges.  Note that above we have closed all file
-           descriptors except std*, so that's safe.  Also note that
-           setuid() when run as root sets the real, effective and
-           saved UIDs. */
-        if (setUser && buildUser) {
-            /* Preserve supplementary groups of the build user, to allow
-               admins to specify groups such as "kvm".  */
-            if (!buildUser->getSupplementaryGIDs().empty() &&
-                setgroups(buildUser->getSupplementaryGIDs().size(),
-                          buildUser->getSupplementaryGIDs().data()) == -1)
-                throw SysError("cannot set supplementary groups of build user");
-
-            if (setgid(buildUser->getGID()) == -1 ||
-                getgid() != buildUser->getGID() ||
-                getegid() != buildUser->getGID())
-                throw SysError("setgid failed");
-
-            if (setuid(buildUser->getUID()) == -1 ||
-                getuid() != buildUser->getUID() ||
-                geteuid() != buildUser->getUID())
-                throw SysError("setuid failed");
-        }
-
-        /* Fill in the arguments. */
-        Strings args;
-
-        const char *builder = "invalid";
-
-        if (drv->isBuiltin()) {
-            ;
-        }
-#if __APPLE__
-        else {
-            /* This has to appear before import statements. */
-            std::string sandboxProfile = "(version 1)\n";
-
-            if (useChroot) {
-
-                /* Lots and lots and lots of file functions freak out if they can't stat their full ancestry */
-                PathSet ancestry;
-
-                /* We build the ancestry before adding all inputPaths to the store because we know they'll
-                   all have the same parents (the store), and there might be lots of inputs. This isn't
-                   particularly efficient... I doubt it'll be a bottleneck in practice */
-                for (auto & i : dirsInChroot) {
-                    Path cur = i.first;
-                    while (cur.compare("/") != 0) {
-                        cur = dirOf(cur);
-                        ancestry.insert(cur);
-                    }
-                }
-
-                /* And we want the store in there regardless of how empty dirsInChroot. We include the innermost
-                   path component this time, since it's typically /nix/store and we care about that. */
-                Path cur = worker.store.storeDir;
-                while (cur.compare("/") != 0) {
-                    ancestry.insert(cur);
-                    cur = dirOf(cur);
-                }
-
-                /* Add all our input paths to the chroot */
-                for (auto & i : inputPaths) {
-                    auto p = worker.store.printStorePath(i);
-                    dirsInChroot[p] = p;
-                }
-
-                /* Violations will go to the syslog if you set this. Unfortunately the destination does not appear to be configurable */
-                if (settings.darwinLogSandboxViolations) {
-                    sandboxProfile += "(deny default)\n";
-                } else {
-                    sandboxProfile += "(deny default (with no-log))\n";
-                }
-
-                sandboxProfile += "(import \"sandbox-defaults.sb\")\n";
-
-                if (derivationIsImpure(derivationType))
-                    sandboxProfile += "(import \"sandbox-network.sb\")\n";
-
-                /* Add the output paths we'll use at build-time to the chroot */
-                sandboxProfile += "(allow file-read* file-write* process-exec\n";
-                for (auto & [_, path] : scratchOutputs)
-                    sandboxProfile += fmt("\t(subpath \"%s\")\n", worker.store.printStorePath(path));
-
-                sandboxProfile += ")\n";
-
-                /* Our inputs (transitive dependencies and any impurities computed above)
-
-                   without file-write* allowed, access() incorrectly returns EPERM
-                 */
-                sandboxProfile += "(allow file-read* file-write* process-exec\n";
-                for (auto & i : dirsInChroot) {
-                    if (i.first != i.second.source)
-                        throw Error(
-                            "can't map '%1%' to '%2%': mismatched impure paths not supported on Darwin",
-                            i.first, i.second.source);
-
-                    string path = i.first;
-                    struct stat st;
-                    if (lstat(path.c_str(), &st)) {
-                        if (i.second.optional && errno == ENOENT)
-                            continue;
-                        throw SysError("getting attributes of path '%s", path);
-                    }
-                    if (S_ISDIR(st.st_mode))
-                        sandboxProfile += fmt("\t(subpath \"%s\")\n", path);
-                    else
-                        sandboxProfile += fmt("\t(literal \"%s\")\n", path);
-                }
-                sandboxProfile += ")\n";
-
-                /* Allow file-read* on full directory hierarchy to self. Allows realpath() */
-                sandboxProfile += "(allow file-read*\n";
-                for (auto & i : ancestry) {
-                    sandboxProfile += fmt("\t(literal \"%s\")\n", i);
-                }
-                sandboxProfile += ")\n";
-
-                sandboxProfile += additionalSandboxProfile;
-            } else
-                sandboxProfile += "(import \"sandbox-minimal.sb\")\n";
-
-            debug("Generated sandbox profile:");
-            debug(sandboxProfile);
-
-            Path sandboxFile = tmpDir + "/.sandbox.sb";
-
-            writeFile(sandboxFile, sandboxProfile);
-
-            bool allowLocalNetworking = parsedDrv->getBoolAttr("__darwinAllowLocalNetworking");
-
-            /* The tmpDir in scope points at the temporary build directory for our derivation. Some packages try different mechanisms
-               to find temporary directories, so we want to open up a broader place for them to dump their files, if needed. */
-            Path globalTmpDir = canonPath(getEnv("TMPDIR").value_or("/tmp"), true);
-
-            /* They don't like trailing slashes on subpath directives */
-            if (globalTmpDir.back() == '/') globalTmpDir.pop_back();
-
-            if (getEnv("_NIX_TEST_NO_SANDBOX") != "1") {
-                builder = "/usr/bin/sandbox-exec";
-                args.push_back("sandbox-exec");
-                args.push_back("-f");
-                args.push_back(sandboxFile);
-                args.push_back("-D");
-                args.push_back("_GLOBAL_TMP_DIR=" + globalTmpDir);
-                args.push_back("-D");
-                args.push_back("IMPORT_DIR=" + settings.nixDataDir + "/nix/sandbox/");
-                if (allowLocalNetworking) {
-                    args.push_back("-D");
-                    args.push_back(string("_ALLOW_LOCAL_NETWORKING=1"));
-                }
-                args.push_back(drv->builder);
-            } else {
-                builder = drv->builder.c_str();
-                args.push_back(std::string(baseNameOf(drv->builder)));
-            }
-        }
-#else
-        else {
-            builder = drv->builder.c_str();
-            args.push_back(std::string(baseNameOf(drv->builder)));
-        }
-#endif
-
-        for (auto & i : drv->args)
-            args.push_back(rewriteStrings(i, inputRewrites));
-
-        /* Indicate that we managed to set up the build environment. */
-        writeFull(STDERR_FILENO, string("\2\n"));
-
-        /* Execute the program.  This should not return. */
-        if (drv->isBuiltin()) {
-            try {
-                logger = makeJSONLogger(*logger);
-
-                BasicDerivation & drv2(*drv);
-                for (auto & e : drv2.env)
-                    e.second = rewriteStrings(e.second, inputRewrites);
-
-                if (drv->builder == "builtin:fetchurl")
-                    builtinFetchurl(drv2, netrcData);
-                else if (drv->builder == "builtin:buildenv")
-                    builtinBuildenv(drv2);
-                else if (drv->builder == "builtin:unpack-channel")
-                    builtinUnpackChannel(drv2);
-                else
-                    throw Error("unsupported builtin function '%1%'", string(drv->builder, 8));
-                _exit(0);
-            } catch (std::exception & e) {
-                writeFull(STDERR_FILENO, e.what() + std::string("\n"));
-                _exit(1);
-            }
-        }
-
-#if __APPLE__
-        posix_spawnattr_t attrp;
-
-        if (posix_spawnattr_init(&attrp))
-            throw SysError("failed to initialize builder");
-
-        if (posix_spawnattr_setflags(&attrp, POSIX_SPAWN_SETEXEC))
-            throw SysError("failed to initialize builder");
-
-        if (drv->platform == "aarch64-darwin") {
-            // Unset kern.curproc_arch_affinity so we can escape Rosetta
-            int affinity = 0;
-            sysctlbyname("kern.curproc_arch_affinity", NULL, NULL, &affinity, sizeof(affinity));
-
-            cpu_type_t cpu = CPU_TYPE_ARM64;
-            posix_spawnattr_setbinpref_np(&attrp, 1, &cpu, NULL);
-        } else if (drv->platform == "x86_64-darwin") {
-            cpu_type_t cpu = CPU_TYPE_X86_64;
-            posix_spawnattr_setbinpref_np(&attrp, 1, &cpu, NULL);
-        }
-
-        posix_spawn(NULL, builder, NULL, &attrp, stringsToCharPtrs(args).data(), stringsToCharPtrs(envStrs).data());
-#else
-        execve(builder, stringsToCharPtrs(args).data(), stringsToCharPtrs(envStrs).data());
-#endif
-
-        throw SysError("executing '%1%'", drv->builder);
-
-    } catch (Error & e) {
-        writeFull(STDERR_FILENO, "\1\n");
-        FdSink sink(STDERR_FILENO);
-        sink << e;
-        sink.flush();
-        _exit(1);
-    }
-}
-
 
 void DerivationGoal::registerOutputs()
 {
@@ -2986,698 +1085,23 @@ void DerivationGoal::registerOutputs()
        We can only early return when the outputs are known a priori. For
        floating content-addressed derivations this isn't the case.
      */
-    if (hook) {
-        bool allValid = true;
-        for (auto & [outputName, outputPath] : worker.store.queryPartialDerivationOutputMap(drvPath)) {
-            if (!outputPath || !worker.store.isValidPath(*outputPath))
-                allValid = false;
-            else
-                finalOutputs.insert_or_assign(outputName, *outputPath);
-        }
-        if (allValid) return;
-    }
-
-    std::map<std::string, ValidPathInfo> infos;
-
-    /* Set of inodes seen during calls to canonicalisePathMetaData()
-       for this build's outputs.  This needs to be shared between
-       outputs to allow hard links between outputs. */
-    InodesSeen inodesSeen;
-
-    Path checkSuffix = ".check";
-    bool keepPreviousRound = settings.keepFailed || settings.runDiffHook;
-
-    std::exception_ptr delayedException;
-
-    /* The paths that can be referenced are the input closures, the
-       output paths, and any paths that have been built via recursive
-       Nix calls. */
-    StorePathSet referenceablePaths;
-    for (auto & p : inputPaths) referenceablePaths.insert(p);
-    for (auto & i : scratchOutputs) referenceablePaths.insert(i.second);
-    for (auto & p : addedPaths) referenceablePaths.insert(p);
-
-    /* FIXME `needsHashRewrite` should probably be removed and we get to the
-       real reason why we aren't using the chroot dir */
-    auto toRealPathChroot = [&](const Path & p) -> Path {
-        return useChroot && !needsHashRewrite()
-            ? chrootRootDir + p
-            : worker.store.toRealPath(p);
-    };
-
-    /* Check whether the output paths were created, and make all
-       output paths read-only.  Then get the references of each output (that we
-       might need to register), so we can topologically sort them. For the ones
-       that are most definitely already installed, we just store their final
-       name so we can also use it in rewrites. */
-    StringSet outputsToSort;
-    struct AlreadyRegistered { StorePath path; };
-    struct PerhapsNeedToRegister { StorePathSet refs; };
-    std::map<std::string, std::variant<AlreadyRegistered, PerhapsNeedToRegister>> outputReferencesIfUnregistered;
-    std::map<std::string, struct stat> outputStats;
-    for (auto & [outputName, _] : drv->outputs) {
-        auto actualPath = toRealPathChroot(worker.store.printStorePath(scratchOutputs.at(outputName)));
-
-        outputsToSort.insert(outputName);
-
-        /* Updated wanted info to remove the outputs we definitely don't need to register */
-        auto & initialInfo = initialOutputs.at(outputName);
-
-        /* Don't register if already valid, and not checking */
-        initialInfo.wanted = buildMode == bmCheck
-            || !(initialInfo.known && initialInfo.known->isValid());
-        if (!initialInfo.wanted) {
-            outputReferencesIfUnregistered.insert_or_assign(
-                outputName,
-                AlreadyRegistered { .path = initialInfo.known->path });
+    for (auto & [outputName, optOutputPath] : worker.store.queryPartialDerivationOutputMap(drvPath)) {
+        if (!wantOutput(outputName, wantedOutputs))
             continue;
-        }
-
-        struct stat st;
-        if (lstat(actualPath.c_str(), &st) == -1) {
-            if (errno == ENOENT)
-                throw BuildError(
-                    "builder for '%s' failed to produce output path for output '%s' at '%s'",
-                    worker.store.printStorePath(drvPath), outputName, actualPath);
-            throw SysError("getting attributes of path '%s'", actualPath);
-        }
-
-#ifndef __CYGWIN__
-        /* Check that the output is not group or world writable, as
-           that means that someone else can have interfered with the
-           build.  Also, the output should be owned by the build
-           user. */
-        if ((!S_ISLNK(st.st_mode) && (st.st_mode & (S_IWGRP | S_IWOTH))) ||
-            (buildUser && st.st_uid != buildUser->getUID()))
+        if (!optOutputPath)
             throw BuildError(
-                    "suspicious ownership or permission on '%s' for output '%s'; rejecting this build output",
-                    actualPath, outputName);
-#endif
-
-        /* Canonicalise first.  This ensures that the path we're
-           rewriting doesn't contain a hard link to /etc/shadow or
-           something like that. */
-        canonicalisePathMetaData(actualPath, buildUser ? buildUser->getUID() : -1, inodesSeen);
-
-        debug("scanning for references for output '%s' in temp location '%s'", outputName, actualPath);
-
-        /* Pass blank Sink as we are not ready to hash data at this stage. */
-        NullSink blank;
-        auto references = worker.store.parseStorePathSet(
-            scanForReferences(blank, actualPath, worker.store.printStorePathSet(referenceablePaths)));
-
-        outputReferencesIfUnregistered.insert_or_assign(
-            outputName,
-            PerhapsNeedToRegister { .refs = references });
-        outputStats.insert_or_assign(outputName, std::move(st));
-    }
-
-    auto sortedOutputNames = topoSort(outputsToSort,
-        {[&](const std::string & name) {
-            return std::visit(overloaded {
-                /* Since we'll use the already installed versions of these, we
-                   can treat them as leaves and ignore any references they
-                   have. */
-                [&](AlreadyRegistered _) { return StringSet {}; },
-                [&](PerhapsNeedToRegister refs) {
-                    StringSet referencedOutputs;
-                    /* FIXME build inverted map up front so no quadratic waste here */
-                    for (auto & r : refs.refs)
-                        for (auto & [o, p] : scratchOutputs)
-                            if (r == p)
-                                referencedOutputs.insert(o);
-                    return referencedOutputs;
-                },
-            }, outputReferencesIfUnregistered.at(name));
-        }},
-        {[&](const std::string & path, const std::string & parent) {
-            // TODO with more -vvvv also show the temporary paths for manual inspection.
-            return BuildError(
-                "cycle detected in build of '%s' in the references of output '%s' from output '%s'",
-                worker.store.printStorePath(drvPath), path, parent);
-        }});
-
-    std::reverse(sortedOutputNames.begin(), sortedOutputNames.end());
-
-    for (auto & outputName : sortedOutputNames) {
-        auto output = drv->outputs.at(outputName);
-        auto & scratchPath = scratchOutputs.at(outputName);
-        auto actualPath = toRealPathChroot(worker.store.printStorePath(scratchPath));
-
-        auto finish = [&](StorePath finalStorePath) {
-            /* Store the final path */
-            finalOutputs.insert_or_assign(outputName, finalStorePath);
-            /* The rewrite rule will be used in downstream outputs that refer to
-               use. This is why the topological sort is essential to do first
-               before this for loop. */
-            if (scratchPath != finalStorePath)
-                outputRewrites[std::string { scratchPath.hashPart() }] = std::string { finalStorePath.hashPart() };
-        };
-
-        std::optional<StorePathSet> referencesOpt = std::visit(overloaded {
-            [&](AlreadyRegistered skippedFinalPath) -> std::optional<StorePathSet> {
-                finish(skippedFinalPath.path);
-                return std::nullopt;
-            },
-            [&](PerhapsNeedToRegister r) -> std::optional<StorePathSet> {
-                return r.refs;
-            },
-        }, outputReferencesIfUnregistered.at(outputName));
-
-        if (!referencesOpt)
-            continue;
-        auto references = *referencesOpt;
-
-        auto rewriteOutput = [&]() {
-            /* Apply hash rewriting if necessary. */
-            if (!outputRewrites.empty()) {
-                warn("rewriting hashes in '%1%'; cross fingers", actualPath);
-
-                /* FIXME: this is in-memory. */
-                StringSink sink;
-                dumpPath(actualPath, sink);
-                deletePath(actualPath);
-                sink.s = make_ref<std::string>(rewriteStrings(*sink.s, outputRewrites));
-                StringSource source(*sink.s);
-                restorePath(actualPath, source);
-
-                /* FIXME: set proper permissions in restorePath() so
-                   we don't have to do another traversal. */
-                canonicalisePathMetaData(actualPath, -1, inodesSeen);
-            }
-        };
-
-        auto rewriteRefs = [&]() -> std::pair<bool, StorePathSet> {
-            /* In the CA case, we need the rewritten refs to calculate the
-               final path, therefore we look for a *non-rewritten
-               self-reference, and use a bool rather try to solve the
-               computationally intractable fixed point. */
-            std::pair<bool, StorePathSet> res {
-                false,
-                {},
-            };
-            for (auto & r : references) {
-                auto name = r.name();
-                auto origHash = std::string { r.hashPart() };
-                if (r == scratchPath)
-                    res.first = true;
-                else if (outputRewrites.count(origHash) == 0)
-                    res.second.insert(r);
-                else {
-                    std::string newRef = outputRewrites.at(origHash);
-                    newRef += '-';
-                    newRef += name;
-                    res.second.insert(StorePath { newRef });
-                }
-            }
-            return res;
-        };
-
-        auto newInfoFromCA = [&](const DerivationOutputCAFloating outputHash) -> ValidPathInfo {
-            auto & st = outputStats.at(outputName);
-            if (outputHash.method == FileIngestionMethod::Flat) {
-                /* The output path should be a regular file without execute permission. */
-                if (!S_ISREG(st.st_mode) || (st.st_mode & S_IXUSR) != 0)
-                    throw BuildError(
-                        "output path '%1%' should be a non-executable regular file "
-                        "since recursive hashing is not enabled (outputHashMode=flat)",
-                        actualPath);
-            }
-            rewriteOutput();
-            /* FIXME optimize and deduplicate with addToStore */
-            std::string oldHashPart { scratchPath.hashPart() };
-            HashModuloSink caSink { outputHash.hashType, oldHashPart };
-            switch (outputHash.method) {
-            case FileIngestionMethod::Recursive:
-                dumpPath(actualPath, caSink);
-                break;
-            case FileIngestionMethod::Flat:
-                readFile(actualPath, caSink);
-                break;
-            }
-            auto got = caSink.finish().first;
-            auto refs = rewriteRefs();
-            HashModuloSink narSink { htSHA256, oldHashPart };
-            dumpPath(actualPath, narSink);
-            auto narHashAndSize = narSink.finish();
-            ValidPathInfo newInfo0 {
-                worker.store.makeFixedOutputPath(
-                    outputHash.method,
-                    got,
-                    outputPathName(drv->name, outputName),
-                    refs.second,
-                    refs.first),
-                narHashAndSize.first,
-            };
-            newInfo0.narSize = narHashAndSize.second;
-            newInfo0.ca = FixedOutputHash {
-                .method = outputHash.method,
-                .hash = got,
-            };
-            newInfo0.references = refs.second;
-            if (refs.first)
-                newInfo0.references.insert(newInfo0.path);
-            if (scratchPath != newInfo0.path) {
-                // Also rewrite the output path
-                auto source = sinkToSource([&](Sink & nextSink) {
-                    StringSink sink;
-                    dumpPath(actualPath, sink);
-                    RewritingSink rsink2(oldHashPart, std::string(newInfo0.path.hashPart()), nextSink);
-                    rsink2(*sink.s);
-                    rsink2.flush();
-                });
-                Path tmpPath = actualPath + ".tmp";
-                restorePath(tmpPath, *source);
-                deletePath(actualPath);
-                movePath(tmpPath, actualPath);
-            }
-
-            assert(newInfo0.ca);
-            return newInfo0;
-        };
-
-        ValidPathInfo newInfo = std::visit(overloaded {
-            [&](DerivationOutputInputAddressed output) {
-                /* input-addressed case */
-                auto requiredFinalPath = output.path;
-                /* Preemptively add rewrite rule for final hash, as that is
-                   what the NAR hash will use rather than normalized-self references */
-                if (scratchPath != requiredFinalPath)
-                    outputRewrites.insert_or_assign(
-                        std::string { scratchPath.hashPart() },
-                        std::string { requiredFinalPath.hashPart() });
-                rewriteOutput();
-                auto narHashAndSize = hashPath(htSHA256, actualPath);
-                ValidPathInfo newInfo0 { requiredFinalPath, narHashAndSize.first };
-                newInfo0.narSize = narHashAndSize.second;
-                auto refs = rewriteRefs();
-                newInfo0.references = refs.second;
-                if (refs.first)
-                    newInfo0.references.insert(newInfo0.path);
-                return newInfo0;
-            },
-            [&](DerivationOutputCAFixed dof) {
-                auto newInfo0 = newInfoFromCA(DerivationOutputCAFloating {
-                    .method = dof.hash.method,
-                    .hashType = dof.hash.hash.type,
-                });
-
-                /* Check wanted hash */
-                Hash & wanted = dof.hash.hash;
-                assert(newInfo0.ca);
-                auto got = getContentAddressHash(*newInfo0.ca);
-                if (wanted != got) {
-                    /* Throw an error after registering the path as
-                       valid. */
-                    worker.hashMismatch = true;
-                    delayedException = std::make_exception_ptr(
-                        BuildError("hash mismatch in fixed-output derivation '%s':\n  specified: %s\n     got:    %s",
-                            worker.store.printStorePath(drvPath),
-                            wanted.to_string(SRI, true),
-                            got.to_string(SRI, true)));
-                }
-                return newInfo0;
-            },
-            [&](DerivationOutputCAFloating dof) {
-                return newInfoFromCA(dof);
-            },
-                [&](DerivationOutputDeferred) {
-                // No derivation should reach that point without having been
-                // rewritten first
-                assert(false);
-                // Ugly, but the compiler insists on having this return a value
-                // of type `ValidPathInfo` despite the `assert(false)`, so
-                // let's provide it
-                return *(ValidPathInfo*)0;
-            },
-        }, output.output);
-
-        /* Calculate where we'll move the output files. In the checking case we
-           will leave leave them where they are, for now, rather than move to
-           their usual "final destination" */
-        auto finalDestPath = worker.store.printStorePath(newInfo.path);
-
-        /* Lock final output path, if not already locked. This happens with
-           floating CA derivations and hash-mismatching fixed-output
-           derivations. */
-        PathLocks dynamicOutputLock;
-        auto optFixedPath = output.path(worker.store, drv->name, outputName);
-        if (!optFixedPath ||
-            worker.store.printStorePath(*optFixedPath) != finalDestPath)
-        {
-            assert(newInfo.ca);
-            dynamicOutputLock.lockPaths({worker.store.toRealPath(finalDestPath)});
-        }
-
-        /* Move files, if needed */
-        if (worker.store.toRealPath(finalDestPath) != actualPath) {
-            if (buildMode == bmRepair) {
-                /* Path already exists, need to replace it */
-                replaceValidPath(worker.store.toRealPath(finalDestPath), actualPath);
-                actualPath = worker.store.toRealPath(finalDestPath);
-            } else if (buildMode == bmCheck) {
-                /* Path already exists, and we want to compare, so we leave out
-                   new path in place. */
-            } else if (worker.store.isValidPath(newInfo.path)) {
-                /* Path already exists because CA path produced by something
-                   else. No moving needed. */
-                assert(newInfo.ca);
-            } else {
-                auto destPath = worker.store.toRealPath(finalDestPath);
-                movePath(actualPath, destPath);
-                actualPath = destPath;
-            }
-        }
-
-        auto localStoreP = dynamic_cast<LocalStore *>(&worker.store);
-        if (!localStoreP)
-            throw Unsupported("can only register outputs with local store, but this is %s", worker.store.getUri());
-        auto & localStore = *localStoreP;
-
-        if (buildMode == bmCheck) {
-
-            if (!worker.store.isValidPath(newInfo.path)) continue;
-            ValidPathInfo oldInfo(*worker.store.queryPathInfo(newInfo.path));
-            if (newInfo.narHash != oldInfo.narHash) {
-                worker.checkMismatch = true;
-                if (settings.runDiffHook || settings.keepFailed) {
-                    auto dst = worker.store.toRealPath(finalDestPath + checkSuffix);
-                    deletePath(dst);
-                    movePath(actualPath, dst);
-
-                    handleDiffHook(
-                        buildUser ? buildUser->getUID() : getuid(),
-                        buildUser ? buildUser->getGID() : getgid(),
-                        finalDestPath, dst, worker.store.printStorePath(drvPath), tmpDir);
-
-                    throw NotDeterministic("derivation '%s' may not be deterministic: output '%s' differs from '%s'",
-                        worker.store.printStorePath(drvPath), worker.store.toRealPath(finalDestPath), dst);
-                } else
-                    throw NotDeterministic("derivation '%s' may not be deterministic: output '%s' differs",
-                        worker.store.printStorePath(drvPath), worker.store.toRealPath(finalDestPath));
-            }
-
-            /* Since we verified the build, it's now ultimately trusted. */
-            if (!oldInfo.ultimate) {
-                oldInfo.ultimate = true;
-                localStore.signPathInfo(oldInfo);
-                localStore.registerValidPaths({{oldInfo.path, oldInfo}});
-            }
-
-            continue;
-        }
-
-        /* For debugging, print out the referenced and unreferenced paths. */
-        for (auto & i : inputPaths) {
-            auto j = references.find(i);
-            if (j == references.end())
-                debug("unreferenced input: '%1%'", worker.store.printStorePath(i));
-            else
-                debug("referenced input: '%1%'", worker.store.printStorePath(i));
-        }
-
-        if (curRound == nrRounds) {
-            localStore.optimisePath(actualPath); // FIXME: combine with scanForReferences()
-            worker.markContentsGood(newInfo.path);
-        }
-
-        newInfo.deriver = drvPath;
-        newInfo.ultimate = true;
-        localStore.signPathInfo(newInfo);
-
-        finish(newInfo.path);
-
-        /* If it's a CA path, register it right away. This is necessary if it
-           isn't statically known so that we can safely unlock the path before
-           the next iteration */
-        if (newInfo.ca)
-            localStore.registerValidPaths({{newInfo.path, newInfo}});
-
-        infos.emplace(outputName, std::move(newInfo));
-    }
-
-    if (buildMode == bmCheck) return;
-
-    /* Apply output checks. */
-    checkOutputs(infos);
-
-    /* Compare the result with the previous round, and report which
-       path is different, if any.*/
-    if (curRound > 1 && prevInfos != infos) {
-        assert(prevInfos.size() == infos.size());
-        for (auto i = prevInfos.begin(), j = infos.begin(); i != prevInfos.end(); ++i, ++j)
-            if (!(*i == *j)) {
-                result.isNonDeterministic = true;
-                Path prev = worker.store.printStorePath(i->second.path) + checkSuffix;
-                bool prevExists = keepPreviousRound && pathExists(prev);
-                hintformat hint = prevExists
-                    ? hintfmt("output '%s' of '%s' differs from '%s' from previous round",
-                        worker.store.printStorePath(i->second.path), worker.store.printStorePath(drvPath), prev)
-                    : hintfmt("output '%s' of '%s' differs from previous round",
-                        worker.store.printStorePath(i->second.path), worker.store.printStorePath(drvPath));
-
-                handleDiffHook(
-                    buildUser ? buildUser->getUID() : getuid(),
-                    buildUser ? buildUser->getGID() : getgid(),
-                    prev, worker.store.printStorePath(i->second.path),
-                    worker.store.printStorePath(drvPath), tmpDir);
-
-                if (settings.enforceDeterminism)
-                    throw NotDeterministic(hint);
-
-                printError(hint);
-
-                curRound = nrRounds; // we know enough, bail out early
-            }
-    }
-
-    /* If this is the first round of several, then move the output out of the way. */
-    if (nrRounds > 1 && curRound == 1 && curRound < nrRounds && keepPreviousRound) {
-        for (auto & [_, outputStorePath] : finalOutputs) {
-            auto path = worker.store.printStorePath(outputStorePath);
-            Path prev = path + checkSuffix;
-            deletePath(prev);
-            Path dst = path + checkSuffix;
-            if (rename(path.c_str(), dst.c_str()))
-                throw SysError("renaming '%s' to '%s'", path, dst);
-        }
-    }
-
-    if (curRound < nrRounds) {
-        prevInfos = std::move(infos);
-        return;
-    }
-
-    /* Remove the .check directories if we're done. FIXME: keep them
-       if the result was not determistic? */
-    if (curRound == nrRounds) {
-        for (auto & [_, outputStorePath] : finalOutputs) {
-            Path prev = worker.store.printStorePath(outputStorePath) + checkSuffix;
-            deletePath(prev);
-        }
-    }
-
-    /* Register each output path as valid, and register the sets of
-       paths referenced by each of them.  If there are cycles in the
-       outputs, this will fail. */
-    {
-        auto localStoreP = dynamic_cast<LocalStore *>(&worker.store);
-        if (!localStoreP)
-            throw Unsupported("can only register outputs with local store, but this is %s", worker.store.getUri());
-        auto & localStore = *localStoreP;
-
-        ValidPathInfos infos2;
-        for (auto & [outputName, newInfo] : infos) {
-            infos2.insert_or_assign(newInfo.path, newInfo);
-        }
-        localStore.registerValidPaths(infos2);
-    }
-
-    /* In case of a fixed-output derivation hash mismatch, throw an
-       exception now that we have registered the output as valid. */
-    if (delayedException)
-        std::rethrow_exception(delayedException);
-
-    /* If we made it this far, we are sure the output matches the derivation
-       (since the delayedException would be a fixed output CA mismatch). That
-       means it's safe to link the derivation to the output hash. We must do
-       that for floating CA derivations, which otherwise couldn't be cached,
-       but it's fine to do in all cases. */
-
-    if (settings.isExperimentalFeatureEnabled("ca-derivations")) {
-        for (auto& [outputName, newInfo] : infos)
-            worker.store.registerDrvOutput(Realisation{
-                .id = DrvOutput{initialOutputs.at(outputName).outputHash, outputName},
-                .outPath = newInfo.path});
-    }
-}
-
-
-void DerivationGoal::checkOutputs(const std::map<Path, ValidPathInfo> & outputs)
-{
-    std::map<Path, const ValidPathInfo &> outputsByPath;
-    for (auto & output : outputs)
-        outputsByPath.emplace(worker.store.printStorePath(output.second.path), output.second);
-
-    for (auto & output : outputs) {
-        auto & outputName = output.first;
-        auto & info = output.second;
-
-        struct Checks
-        {
-            bool ignoreSelfRefs = false;
-            std::optional<uint64_t> maxSize, maxClosureSize;
-            std::optional<Strings> allowedReferences, allowedRequisites, disallowedReferences, disallowedRequisites;
-        };
-
-        /* Compute the closure and closure size of some output. This
-           is slightly tricky because some of its references (namely
-           other outputs) may not be valid yet. */
-        auto getClosure = [&](const StorePath & path)
-        {
-            uint64_t closureSize = 0;
-            StorePathSet pathsDone;
-            std::queue<StorePath> pathsLeft;
-            pathsLeft.push(path);
-
-            while (!pathsLeft.empty()) {
-                auto path = pathsLeft.front();
-                pathsLeft.pop();
-                if (!pathsDone.insert(path).second) continue;
-
-                auto i = outputsByPath.find(worker.store.printStorePath(path));
-                if (i != outputsByPath.end()) {
-                    closureSize += i->second.narSize;
-                    for (auto & ref : i->second.references)
-                        pathsLeft.push(ref);
-                } else {
-                    auto info = worker.store.queryPathInfo(path);
-                    closureSize += info->narSize;
-                    for (auto & ref : info->references)
-                        pathsLeft.push(ref);
-                }
-            }
-
-            return std::make_pair(std::move(pathsDone), closureSize);
-        };
-
-        auto applyChecks = [&](const Checks & checks)
-        {
-            if (checks.maxSize && info.narSize > *checks.maxSize)
-                throw BuildError("path '%s' is too large at %d bytes; limit is %d bytes",
-                    worker.store.printStorePath(info.path), info.narSize, *checks.maxSize);
-
-            if (checks.maxClosureSize) {
-                uint64_t closureSize = getClosure(info.path).second;
-                if (closureSize > *checks.maxClosureSize)
-                    throw BuildError("closure of path '%s' is too large at %d bytes; limit is %d bytes",
-                        worker.store.printStorePath(info.path), closureSize, *checks.maxClosureSize);
-            }
-
-            auto checkRefs = [&](const std::optional<Strings> & value, bool allowed, bool recursive)
-            {
-                if (!value) return;
-
-                /* Parse a list of reference specifiers.  Each element must
-                   either be a store path, or the symbolic name of the output
-                   of the derivation (such as `out'). */
-                StorePathSet spec;
-                for (auto & i : *value) {
-                    if (worker.store.isStorePath(i))
-                        spec.insert(worker.store.parseStorePath(i));
-                    else if (finalOutputs.count(i))
-                        spec.insert(finalOutputs.at(i));
-                    else throw BuildError("derivation contains an illegal reference specifier '%s'", i);
-                }
-
-                auto used = recursive
-                    ? getClosure(info.path).first
-                    : info.references;
-
-                if (recursive && checks.ignoreSelfRefs)
-                    used.erase(info.path);
-
-                StorePathSet badPaths;
-
-                for (auto & i : used)
-                    if (allowed) {
-                        if (!spec.count(i))
-                            badPaths.insert(i);
-                    } else {
-                        if (spec.count(i))
-                            badPaths.insert(i);
-                    }
-
-                if (!badPaths.empty()) {
-                    string badPathsStr;
-                    for (auto & i : badPaths) {
-                        badPathsStr += "\n  ";
-                        badPathsStr += worker.store.printStorePath(i);
-                    }
-                    throw BuildError("output '%s' is not allowed to refer to the following paths:%s",
-                        worker.store.printStorePath(info.path), badPathsStr);
-                }
-            };
-
-            checkRefs(checks.allowedReferences, true, false);
-            checkRefs(checks.allowedRequisites, true, true);
-            checkRefs(checks.disallowedReferences, false, false);
-            checkRefs(checks.disallowedRequisites, false, true);
-        };
-
-        if (auto structuredAttrs = parsedDrv->getStructuredAttrs()) {
-            auto outputChecks = structuredAttrs->find("outputChecks");
-            if (outputChecks != structuredAttrs->end()) {
-                auto output = outputChecks->find(outputName);
-
-                if (output != outputChecks->end()) {
-                    Checks checks;
-
-                    auto maxSize = output->find("maxSize");
-                    if (maxSize != output->end())
-                        checks.maxSize = maxSize->get<uint64_t>();
-
-                    auto maxClosureSize = output->find("maxClosureSize");
-                    if (maxClosureSize != output->end())
-                        checks.maxClosureSize = maxClosureSize->get<uint64_t>();
-
-                    auto get = [&](const std::string & name) -> std::optional<Strings> {
-                        auto i = output->find(name);
-                        if (i != output->end()) {
-                            Strings res;
-                            for (auto j = i->begin(); j != i->end(); ++j) {
-                                if (!j->is_string())
-                                    throw Error("attribute '%s' of derivation '%s' must be a list of strings", name, worker.store.printStorePath(drvPath));
-                                res.push_back(j->get<std::string>());
-                            }
-                            checks.disallowedRequisites = res;
-                            return res;
-                        }
-                        return {};
-                    };
-
-                    checks.allowedReferences = get("allowedReferences");
-                    checks.allowedRequisites = get("allowedRequisites");
-                    checks.disallowedReferences = get("disallowedReferences");
-                    checks.disallowedRequisites = get("disallowedRequisites");
+                "output '%s' from derivation '%s' does not have a known output path",
+                outputName, worker.store.printStorePath(drvPath));
+        auto & outputPath = *optOutputPath;
+        if (!worker.store.isValidPath(outputPath))
+            throw BuildError(
+                "output '%s' from derivation '%s' is supposed to be at '%s' but that path is not valid",
+                outputName, worker.store.printStorePath(drvPath), worker.store.printStorePath(outputPath));
 
-                    applyChecks(checks);
-                }
-            }
-        } else {
-            // legacy non-structured-attributes case
-            Checks checks;
-            checks.ignoreSelfRefs = true;
-            checks.allowedReferences = parsedDrv->getStringsAttr("allowedReferences");
-            checks.allowedRequisites = parsedDrv->getStringsAttr("allowedRequisites");
-            checks.disallowedReferences = parsedDrv->getStringsAttr("disallowedReferences");
-            checks.disallowedRequisites = parsedDrv->getStringsAttr("disallowedRequisites");
-            applyChecks(checks);
-        }
+        finalOutputs.insert_or_assign(outputName, outputPath);
     }
 }
 
-
 Path DerivationGoal::openLogFile()
 {
     logSize = 0;
@@ -3722,26 +1146,15 @@ void DerivationGoal::closeLogFile()
 }
 
 
-void DerivationGoal::deleteTmpDir(bool force)
+bool DerivationGoal::isReadDesc(int fd)
 {
-    if (tmpDir != "") {
-        /* Don't keep temporary directories for builtins because they
-           might have privileged stuff (like a copy of netrc). */
-        if (settings.keepFailed && !force && !drv->isBuiltin()) {
-            printError("note: keeping build directory '%s'", tmpDir);
-            chmod(tmpDir.c_str(), 0755);
-        }
-        else
-            deletePath(tmpDir);
-        tmpDir = "";
-    }
+    return fd == hook->builderOut.readSide.get();
 }
 
 
 void DerivationGoal::handleChildOutput(int fd, const string & data)
 {
-    if ((hook && fd == hook->builderOut.readSide.get()) ||
-        (!hook && fd == builderOut.readSide.get()))
+    if (isReadDesc(fd))
     {
         logSize += data.size();
         if (settings.maxLogSize && logSize > settings.maxLogSize) {
@@ -3857,22 +1270,6 @@ void DerivationGoal::checkPathValidity()
 }
 
 
-StorePath DerivationGoal::makeFallbackPath(std::string_view outputName)
-{
-    return worker.store.makeStorePath(
-        "rewrite:" + std::string(drvPath.to_string()) + ":name:" + std::string(outputName),
-        Hash(htSHA256), outputPathName(drv->name, outputName));
-}
-
-
-StorePath DerivationGoal::makeFallbackPath(const StorePath & path)
-{
-    return worker.store.makeStorePath(
-        "rewrite:" + std::string(drvPath.to_string()) + ":" + std::string(path.to_string()),
-        Hash(htSHA256), path.name());
-}
-
-
 void DerivationGoal::done(BuildResult::Status status, std::optional<Error> ex)
 {
     result.status = status;
diff --git a/src/libstore/build/derivation-goal.hh b/src/libstore/build/derivation-goal.hh
index 6dc164922..c85bcd84f 100644
--- a/src/libstore/build/derivation-goal.hh
+++ b/src/libstore/build/derivation-goal.hh
@@ -2,7 +2,8 @@
 
 #include "parsed-derivations.hh"
 #include "lock.hh"
-#include "local-store.hh"
+#include "store-api.hh"
+#include "pathlocks.hh"
 #include "goal.hh"
 
 namespace nix {
@@ -79,18 +80,6 @@ struct DerivationGoal : public Goal
 
     std::map<std::string, InitialOutput> initialOutputs;
 
-    /* User selected for running the builder. */
-    std::unique_ptr<UserLock> buildUser;
-
-    /* The process ID of the builder. */
-    Pid pid;
-
-    /* The temporary directory. */
-    Path tmpDir;
-
-    /* The path of the temporary directory in the sandbox. */
-    Path tmpDirInSandbox;
-
     /* File descriptor for the log file. */
     AutoCloseFD fdLogFile;
     std::shared_ptr<BufferedSink> logFileSink, logSink;
@@ -106,79 +95,15 @@ struct DerivationGoal : public Goal
 
     std::string currentHookLine;
 
-    /* Pipe for the builder's standard output/error. */
-    Pipe builderOut;
-
-    /* Pipe for synchronising updates to the builder namespaces. */
-    Pipe userNamespaceSync;
-
-    /* The mount namespace of the builder, used to add additional
-       paths to the sandbox as a result of recursive Nix calls. */
-    AutoCloseFD sandboxMountNamespace;
-
-    /* On Linux, whether we're doing the build in its own user
-       namespace. */
-    bool usingUserNamespace = true;
-
     /* The build hook. */
     std::unique_ptr<HookInstance> hook;
 
-    /* Whether we're currently doing a chroot build. */
-    bool useChroot = false;
-
-    Path chrootRootDir;
-
-    /* RAII object to delete the chroot directory. */
-    std::shared_ptr<AutoDelete> autoDelChroot;
-
     /* The sort of derivation we are building. */
     DerivationType derivationType;
 
-    /* Whether to run the build in a private network namespace. */
-    bool privateNetwork = false;
-
     typedef void (DerivationGoal::*GoalState)();
     GoalState state;
 
-    /* Stuff we need to pass to initChild(). */
-    struct ChrootPath {
-        Path source;
-        bool optional;
-        ChrootPath(Path source = "", bool optional = false)
-            : source(source), optional(optional)
-        { }
-    };
-    typedef map<Path, ChrootPath> DirsInChroot; // maps target path to source path
-    DirsInChroot dirsInChroot;
-
-    typedef map<string, string> Environment;
-    Environment env;
-
-#if __APPLE__
-    typedef string SandboxProfile;
-    SandboxProfile additionalSandboxProfile;
-#endif
-
-    /* Hash rewriting. */
-    StringMap inputRewrites, outputRewrites;
-    typedef map<StorePath, StorePath> RedirectedOutputs;
-    RedirectedOutputs redirectedOutputs;
-
-    /* The outputs paths used during the build.
-
-       - Input-addressed derivations or fixed content-addressed outputs are
-         sometimes built when some of their outputs already exist, and can not
-         be hidden via sandboxing. We use temporary locations instead and
-         rewrite after the build. Otherwise the regular predetermined paths are
-         put here.
-
-       - Floating content-addressed derivations do not know their final build
-         output paths until the outputs are hashed, so random locations are
-         used, and then renamed. The randomness helps guard against hidden
-         self-references.
-     */
-    OutputPathMap scratchOutputs;
-
     /* The final output paths of the build.
 
        - For input-addressed derivations, always the precomputed paths
@@ -191,11 +116,6 @@ struct DerivationGoal : public Goal
 
     BuildMode buildMode;
 
-    /* If we're repairing without a chroot, there may be outputs that
-       are valid but corrupt.  So we redirect these outputs to
-       temporary paths. */
-    StorePathSet redirectedBadOutputs;
-
     BuildResult result;
 
     /* The current round, if we're building multiple times. */
@@ -203,17 +123,6 @@ struct DerivationGoal : public Goal
 
     size_t nrRounds;
 
-    /* Path registration info from the previous round, if we're
-       building multiple times. Since this contains the hash, it
-       allows us to compare whether two rounds produced the same
-       result. */
-    std::map<Path, ValidPathInfo> prevInfos;
-
-    uid_t sandboxUid() { return usingUserNamespace ? 1000 : buildUser->getUID(); }
-    gid_t sandboxGid() { return usingUserNamespace ?  100 : buildUser->getGID(); }
-
-    const static Path homeDir;
-
     std::unique_ptr<MaintainCount<uint64_t>> mcExpectedBuilds, mcRunningBuilds;
 
     std::unique_ptr<Activity> act;
@@ -226,39 +135,13 @@ struct DerivationGoal : public Goal
     /* The remote machine on which we're building. */
     std::string machineName;
 
-    /* The recursive Nix daemon socket. */
-    AutoCloseFD daemonSocket;
-
-    /* The daemon main thread. */
-    std::thread daemonThread;
-
-    /* The daemon worker threads. */
-    std::vector<std::thread> daemonWorkerThreads;
-
-    /* Paths that were added via recursive Nix calls. */
-    StorePathSet addedPaths;
-
-    /* Recursive Nix calls are only allowed to build or realize paths
-       in the original input closure or added via a recursive Nix call
-       (so e.g. you can't do 'nix-store -r /nix/store/<bla>' where
-       /nix/store/<bla> is some arbitrary path in a binary cache). */
-    bool isAllowed(const StorePath & path)
-    {
-        return inputPaths.count(path) || addedPaths.count(path);
-    }
-
-    friend struct RestrictedStore;
-
     DerivationGoal(const StorePath & drvPath,
         const StringSet & wantedOutputs, Worker & worker,
         BuildMode buildMode = bmNormal);
     DerivationGoal(const StorePath & drvPath, const BasicDerivation & drv,
         const StringSet & wantedOutputs, Worker & worker,
         BuildMode buildMode = bmNormal);
-    ~DerivationGoal();
-
-    /* Whether we need to perform hash rewriting if there are valid output paths. */
-    bool needsHashRewrite();
+    virtual ~DerivationGoal();
 
     void timedOut(Error && ex) override;
 
@@ -280,7 +163,7 @@ struct DerivationGoal : public Goal
     void closureRepaired();
     void inputsRealised();
     void tryToBuild();
-    void tryLocalBuild();
+    virtual void tryLocalBuild();
     void buildDone();
 
     void resolvedFinished();
@@ -288,40 +171,11 @@ struct DerivationGoal : public Goal
     /* Is the build hook willing to perform the build? */
     HookReply tryBuildHook();
 
-    /* Start building a derivation. */
-    void startBuilder();
-
-    /* Fill in the environment for the builder. */
-    void initEnv();
-
-    /* Setup tmp dir location. */
-    void initTmpDir();
-
-    /* Write a JSON file containing the derivation attributes. */
-    void writeStructuredAttrs();
-
-    void startDaemon();
-
-    void stopDaemon();
-
-    /* Add 'path' to the set of paths that may be referenced by the
-       outputs, and make it appear in the sandbox. */
-    void addDependency(const StorePath & path);
-
-    /* Make a file owned by the builder. */
-    void chownToBuilder(const Path & path);
-
-    /* Run the builder's process. */
-    void runChild();
+    virtual int getChildStatus();
 
     /* Check that the derivation outputs all exist and register them
        as valid. */
-    void registerOutputs();
-
-    /* Check that an output meets the requirements specified by the
-       'outputChecks' attribute (or the legacy
-       '{allowed,disallowed}{References,Requisites}' attributes). */
-    void checkOutputs(const std::map<std::string, ValidPathInfo> & outputs);
+    virtual void registerOutputs();
 
     /* Open a log file and a pipe to it. */
     Path openLogFile();
@@ -329,8 +183,18 @@ struct DerivationGoal : public Goal
     /* Close the log file. */
     void closeLogFile();
 
-    /* Delete the temporary directory, if we have one. */
-    void deleteTmpDir(bool force);
+    /* Close the read side of the logger pipe. */
+    virtual void closeReadPipes();
+
+    /* Cleanup hooks for buildDone() */
+    virtual void cleanupHookFinally();
+    virtual void cleanupPreChildKill();
+    virtual void cleanupPostChildKill();
+    virtual bool cleanupDecideWhetherDiskFull();
+    virtual void cleanupPostOutputsRegisteredModeCheck();
+    virtual void cleanupPostOutputsRegisteredModeNonCheck();
+
+    virtual bool isReadDesc(int fd);
 
     /* Callback used by the worker to write to the log. */
     void handleChildOutput(int fd, const string & data) override;
@@ -347,17 +211,7 @@ struct DerivationGoal : public Goal
     void checkPathValidity();
 
     /* Forcibly kill the child process, if any. */
-    void killChild();
-
-    /* Create alternative path calculated from but distinct from the
-       input, so we can avoid overwriting outputs (or other store paths)
-       that already exist. */
-    StorePath makeFallbackPath(const StorePath & path);
-    /* Make a path to another based on the output name along with the
-       derivation hash. */
-    /* FIXME add option to randomize, so we can audit whether our
-       rewrites caught everything */
-    StorePath makeFallbackPath(std::string_view outputName);
+    virtual void killChild();
 
     void repairClosure();
 
@@ -370,4 +224,6 @@ struct DerivationGoal : public Goal
     StorePathSet exportReferences(const StorePathSet & storePaths);
 };
 
+MakeError(NotDeterministic, BuildError);
+
 }
diff --git a/src/libstore/build/entry-points.cc b/src/libstore/build/entry-points.cc
index 3a05a022c..01a564aba 100644
--- a/src/libstore/build/entry-points.cc
+++ b/src/libstore/build/entry-points.cc
@@ -2,6 +2,7 @@
 #include "worker.hh"
 #include "substitution-goal.hh"
 #include "derivation-goal.hh"
+#include "local-store.hh"
 
 namespace nix {
 
diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 924c69fb7..23ffe740a 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -1,4 +1,4 @@
-#include "derivation-goal.hh"
+#include "local-derivation-goal.hh"
 #include "hook-instance.hh"
 #include "worker.hh"
 #include "builtins.hh"
@@ -75,7 +75,6 @@ void handleDiffHook(
             diffHookOptions.uid = uid;
             diffHookOptions.gid = gid;
             diffHookOptions.chdir = "/";
-
             auto diffRes = runProgram(diffHookOptions);
             if (!statusOk(diffRes.first))
                 throw ExecError(diffRes.first,
@@ -94,8 +93,9 @@ void handleDiffHook(
     }
 }
 
-const Path DerivationGoal::homeDir = "/homeless-shelter";
+const Path LocalDerivationGoal::homeDir = "/homeless-shelter";
 
+#if 0
 DerivationGoal::DerivationGoal(const StorePath & drvPath,
     const StringSet & wantedOutputs, Worker & worker, BuildMode buildMode)
     : Goal(worker)
@@ -138,19 +138,20 @@ DerivationGoal::DerivationGoal(const StorePath & drvPath, const BasicDerivation
        garbage-collected. (See isActiveTempFile() in gc.cc.) */
     worker.store.addTempRoot(this->drvPath);
 }
+#endif
 
 
-DerivationGoal::~DerivationGoal()
+LocalDerivationGoal::~LocalDerivationGoal()
 {
     /* Careful: we should never ever throw an exception from a
        destructor. */
+    try { deleteTmpDir(false); } catch (...) { ignoreException(); }
     try { killChild(); } catch (...) { ignoreException(); }
     try { stopDaemon(); } catch (...) { ignoreException(); }
-    try { deleteTmpDir(false); } catch (...) { ignoreException(); }
-    try { closeLogFile(); } catch (...) { ignoreException(); }
 }
 
 
+#if 0
 string DerivationGoal::key()
 {
     /* Ensure that derivations get built in order of their name,
@@ -159,9 +160,10 @@ string DerivationGoal::key()
        derivation goals (due to "b$"). */
     return "b$" + std::string(drvPath.name()) + "$" + worker.store.printStorePath(drvPath);
 }
+#endif
 
 
-inline bool DerivationGoal::needsHashRewrite()
+inline bool LocalDerivationGoal::needsHashRewrite()
 {
 #if __linux__
     return !useChroot;
@@ -172,7 +174,15 @@ inline bool DerivationGoal::needsHashRewrite()
 }
 
 
-void DerivationGoal::killChild()
+LocalStore & LocalDerivationGoal::getLocalStore()
+{
+    auto p = dynamic_cast<LocalStore *>(&worker.store);
+    assert(p);
+    return *p;
+}
+
+
+void LocalDerivationGoal::killChild()
 {
     if (pid != -1) {
         worker.childTerminated(this);
@@ -193,17 +203,11 @@ void DerivationGoal::killChild()
         assert(pid == -1);
     }
 
-    hook.reset();
-}
-
-
-void DerivationGoal::timedOut(Error && ex)
-{
-    killChild();
-    done(BuildResult::TimedOut, ex);
+    DerivationGoal::killChild();
 }
 
 
+#if 0
 void DerivationGoal::work()
 {
     (this->*state)();
@@ -695,15 +699,9 @@ void DerivationGoal::tryToBuild()
     state = &DerivationGoal::tryLocalBuild;
     worker.wakeUp(shared_from_this());
 }
+#endif
 
-void DerivationGoal::tryLocalBuild() {
-    /* Make sure that we are allowed to start a build. */
-    if (!dynamic_cast<LocalStore *>(&worker.store)) {
-        throw Error(
-            "unable to build with a primary store that isn't a local store; "
-            "either pass a different '--store' or enable remote builds."
-            "\nhttps://nixos.org/nix/manual/#chap-distributed-builds");
-    }
+void LocalDerivationGoal::tryLocalBuild() {
     unsigned int curBuilds = worker.getNrLocalBuilds();
     if (curBuilds >= settings.maxBuildJobs) {
         worker.waitForBuildSlot(shared_from_this());
@@ -757,7 +755,6 @@ void DerivationGoal::tryLocalBuild() {
     started();
 }
 
-
 static void chmod_(const Path & path, mode_t mode)
 {
     if (chmod(path.c_str(), mode) == -1)
@@ -785,51 +782,125 @@ static void movePath(const Path & src, const Path & dst)
 }
 
 
-void replaceValidPath(const Path & storePath, const Path & tmpPath)
+extern void replaceValidPath(const Path & storePath, const Path & tmpPath);
+
+
+int LocalDerivationGoal::getChildStatus()
 {
-    /* We can't atomically replace storePath (the original) with
-       tmpPath (the replacement), so we have to move it out of the
-       way first.  We'd better not be interrupted here, because if
-       we're repairing (say) Glibc, we end up with a broken system. */
-    Path oldPath = (format("%1%.old-%2%-%3%") % storePath % getpid() % random()).str();
-    if (pathExists(storePath))
-        movePath(storePath, oldPath);
+    return hook ? DerivationGoal::getChildStatus() : pid.kill();
+}
 
-    try {
-        movePath(tmpPath, storePath);
-    } catch (...) {
-        try {
-            // attempt to recover
-            movePath(oldPath, storePath);
-        } catch (...) {
-            ignoreException();
+void LocalDerivationGoal::closeReadPipes()
+{
+    if (hook) {
+        DerivationGoal::closeReadPipes();
+    } else
+        builderOut.readSide = -1;
+}
+
+
+void LocalDerivationGoal::cleanupHookFinally()
+{
+    /* Release the build user at the end of this function. We don't do
+       it right away because we don't want another build grabbing this
+       uid and then messing around with our output. */
+    buildUser.reset();
+}
+
+
+void LocalDerivationGoal::cleanupPreChildKill()
+{
+    sandboxMountNamespace = -1;
+}
+
+
+void LocalDerivationGoal::cleanupPostChildKill()
+{
+    /* When running under a build user, make sure that all processes
+       running under that uid are gone.  This is to prevent a
+       malicious user from leaving behind a process that keeps files
+       open and modifies them after they have been chown'ed to
+       root. */
+    if (buildUser) buildUser->kill();
+
+    /* Terminate the recursive Nix daemon. */
+    stopDaemon();
+}
+
+
+bool LocalDerivationGoal::cleanupDecideWhetherDiskFull()
+{
+    bool diskFull = false;
+
+    /* Heuristically check whether the build failure may have
+       been caused by a disk full condition.  We have no way
+       of knowing whether the build actually got an ENOSPC.
+       So instead, check if the disk is (nearly) full now.  If
+       so, we don't mark this build as a permanent failure. */
+#if HAVE_STATVFS
+	{
+        auto & localStore = getLocalStore();
+        uint64_t required = 8ULL * 1024 * 1024; // FIXME: make configurable
+        struct statvfs st;
+        if (statvfs(localStore.realStoreDir.c_str(), &st) == 0 &&
+            (uint64_t) st.f_bavail * st.f_bsize < required)
+            diskFull = true;
+        if (statvfs(tmpDir.c_str(), &st) == 0 &&
+            (uint64_t) st.f_bavail * st.f_bsize < required)
+            diskFull = true;
+	}
+#endif
+
+    deleteTmpDir(false);
+
+    /* Move paths out of the chroot for easier debugging of
+       build failures. */
+    if (useChroot && buildMode == bmNormal)
+        for (auto & [_, status] : initialOutputs) {
+            if (!status.known) continue;
+            if (buildMode != bmCheck && status.known->isValid()) continue;
+            auto p = worker.store.printStorePath(status.known->path);
+            if (pathExists(chrootRootDir + p))
+                rename((chrootRootDir + p).c_str(), p.c_str());
         }
-        throw;
-    }
 
-    deletePath(oldPath);
+    return diskFull;
+}
+
+
+void LocalDerivationGoal::cleanupPostOutputsRegisteredModeCheck()
+{
+    deleteTmpDir(true);
 }
 
 
-MakeError(NotDeterministic, BuildError);
+void LocalDerivationGoal::cleanupPostOutputsRegisteredModeNonCheck()
+{
+    /* Delete unused redirected outputs (when doing hash rewriting). */
+    for (auto & i : redirectedOutputs)
+        deletePath(worker.store.Store::toRealPath(i.second));
+
+    /* Delete the chroot (if we were using one). */
+    autoDelChroot.reset(); /* this runs the destructor */
+
+    cleanupPostOutputsRegisteredModeCheck();
+}
 
 
+#if 0
 void DerivationGoal::buildDone()
 {
     trace("build done");
 
-    /* Release the build user at the end of this function. We don't do
-       it right away because we don't want another build grabbing this
-       uid and then messing around with our output. */
-    Finally releaseBuildUser([&]() { buildUser.reset(); });
+    Finally releaseBuildUser([&](){ this->cleanupHookFinally(); });
 
-    sandboxMountNamespace = -1;
+    cleanupPreChildKill();
 
     /* Since we got an EOF on the logger pipe, the builder is presumed
        to have terminated.  In fact, the builder could also have
        simply have closed its end of the pipe, so just to be sure,
        kill it. */
-    int status = hook ? hook->pid.kill() : pid.kill();
+    int status = getChildStatus();
 
     debug("builder process for '%s' finished", worker.store.printStorePath(drvPath));
 
@@ -840,24 +911,12 @@ void DerivationGoal::buildDone()
     worker.childTerminated(this);
 
     /* Close the read side of the logger pipe. */
-    if (hook) {
-        hook->builderOut.readSide = -1;
-        hook->fromHook.readSide = -1;
-    } else
-        builderOut.readSide = -1;
+    closeReadPipes();
 
     /* Close the log file. */
     closeLogFile();
 
-    /* When running under a build user, make sure that all processes
-       running under that uid are gone.  This is to prevent a
-       malicious user from leaving behind a process that keeps files
-       open and modifies them after they have been chown'ed to
-       root. */
-    if (buildUser) buildUser->kill();
-
-    /* Terminate the recursive Nix daemon. */
-    stopDaemon();
+    cleanupPostChildKill();
 
     bool diskFull = false;
 
@@ -866,36 +925,7 @@ void DerivationGoal::buildDone()
         /* Check the exit status. */
         if (!statusOk(status)) {
 
-            /* Heuristically check whether the build failure may have
-               been caused by a disk full condition.  We have no way
-               of knowing whether the build actually got an ENOSPC.
-               So instead, check if the disk is (nearly) full now.  If
-               so, we don't mark this build as a permanent failure. */
-#if HAVE_STATVFS
-            if (auto localStore = dynamic_cast<LocalStore *>(&worker.store)) {
-                uint64_t required = 8ULL * 1024 * 1024; // FIXME: make configurable
-                struct statvfs st;
-                if (statvfs(localStore->realStoreDir.c_str(), &st) == 0 &&
-                    (uint64_t) st.f_bavail * st.f_bsize < required)
-                    diskFull = true;
-                if (statvfs(tmpDir.c_str(), &st) == 0 &&
-                    (uint64_t) st.f_bavail * st.f_bsize < required)
-                    diskFull = true;
-            }
-#endif
-
-            deleteTmpDir(false);
-
-            /* Move paths out of the chroot for easier debugging of
-               build failures. */
-            if (useChroot && buildMode == bmNormal)
-                for (auto & [_, status] : initialOutputs) {
-                    if (!status.known) continue;
-                    if (buildMode != bmCheck && status.known->isValid()) continue;
-                    auto p = worker.store.printStorePath(status.known->path);
-                    if (pathExists(chrootRootDir + p))
-                        rename((chrootRootDir + p).c_str(), p.c_str());
-                }
+            diskFull |= cleanupDecideWhetherDiskFull();
 
             auto msg = fmt("builder for '%s' %s",
                 yellowtxt(worker.store.printStorePath(drvPath)),
@@ -975,19 +1005,12 @@ void DerivationGoal::buildDone()
         }
 
         if (buildMode == bmCheck) {
-            deleteTmpDir(true);
+            cleanupPostOutputsRegisteredModeCheck();
             done(BuildResult::Built);
             return;
         }
 
-        /* Delete unused redirected outputs (when doing hash rewriting). */
-        for (auto & i : redirectedOutputs)
-            deletePath(worker.store.Store::toRealPath(i.second));
-
-        /* Delete the chroot (if we were using one). */
-        autoDelChroot.reset(); /* this runs the destructor */
-
-        deleteTmpDir(true);
+        cleanupPostOutputsRegisteredModeNonCheck();
 
         /* Repeat the build if necessary. */
         if (curRound++ < nrRounds) {
@@ -1169,15 +1192,17 @@ HookReply DerivationGoal::tryBuildHook()
 
     return rpAccept;
 }
+#endif
 
 
 int childEntry(void * arg)
 {
-    ((DerivationGoal *) arg)->runChild();
+    ((LocalDerivationGoal *) arg)->runChild();
     return 1;
 }
 
 
+#if 0
 StorePathSet DerivationGoal::exportReferences(const StorePathSet & storePaths)
 {
     StorePathSet paths;
@@ -1212,6 +1237,7 @@ StorePathSet DerivationGoal::exportReferences(const StorePathSet & storePaths)
 
     return paths;
 }
+#endif
 
 static std::once_flag dns_resolve_flag;
 
@@ -1230,7 +1256,7 @@ static void preloadNSS() {
 }
 
 
-void linkOrCopy(const Path & from, const Path & to)
+static void linkOrCopy(const Path & from, const Path & to)
 {
     if (link(from.c_str(), to.c_str()) == -1) {
         /* Hard-linking fails if we exceed the maximum link count on a
@@ -1247,7 +1273,7 @@ void linkOrCopy(const Path & from, const Path & to)
 }
 
 
-void DerivationGoal::startBuilder()
+void LocalDerivationGoal::startBuilder()
 {
     /* Right platform? */
     if (!parsedDrv->canBuildLocally(worker.store))
@@ -1285,15 +1311,13 @@ void DerivationGoal::startBuilder()
             useChroot = !(derivationIsImpure(derivationType)) && !noChroot;
     }
 
-    if (auto localStoreP = dynamic_cast<LocalStore *>(&worker.store)) {
-        auto & localStore = *localStoreP;
-        if (localStore.storeDir != localStore.realStoreDir) {
-            #if __linux__
-                useChroot = true;
-            #else
-                throw Error("building using a diverted store is not supported on this platform");
-            #endif
-        }
+    auto & localStore = getLocalStore();
+    if (localStore.storeDir != localStore.realStoreDir) {
+        #if __linux__
+            useChroot = true;
+        #else
+            throw Error("building using a diverted store is not supported on this platform");
+        #endif
     }
 
     /* Create a temporary directory where the build will take
@@ -1850,7 +1874,7 @@ void DerivationGoal::startBuilder()
 }
 
 
-void DerivationGoal::initTmpDir() {
+void LocalDerivationGoal::initTmpDir() {
     /* In a sandbox, for determinism, always use the same temporary
        directory. */
 #if __linux__
@@ -1899,7 +1923,7 @@ void DerivationGoal::initTmpDir() {
 }
 
 
-void DerivationGoal::initEnv()
+void LocalDerivationGoal::initEnv()
 {
     env.clear();
 
@@ -1960,7 +1984,7 @@ void DerivationGoal::initEnv()
 static std::regex shVarName("[A-Za-z_][A-Za-z0-9_]*");
 
 
-void DerivationGoal::writeStructuredAttrs()
+void LocalDerivationGoal::writeStructuredAttrs()
 {
     auto structuredAttrs = parsedDrv->getStructuredAttrs();
     if (!structuredAttrs) return;
@@ -2079,9 +2103,9 @@ struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual Lo
 {
     ref<LocalStore> next;
 
-    DerivationGoal & goal;
+    LocalDerivationGoal & goal;
 
-    RestrictedStore(const Params & params, ref<LocalStore> next, DerivationGoal & goal)
+    RestrictedStore(const Params & params, ref<LocalStore> next, LocalDerivationGoal & goal)
         : StoreConfig(params)
         , LocalFSStoreConfig(params)
         , RestrictedStoreConfig(params)
@@ -2256,15 +2280,14 @@ struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual Lo
 };
 
 
-void DerivationGoal::startDaemon()
+void LocalDerivationGoal::startDaemon()
 {
     settings.requireExperimentalFeature("recursive-nix");
 
     Store::Params params;
     params["path-info-cache-size"] = "0";
     params["store"] = worker.store.storeDir;
-    if (auto localStore = dynamic_cast<LocalStore *>(&worker.store))
-        params["root"] = localStore->rootDir;
+    params["root"] = getLocalStore().rootDir;
     params["state"] = "/no-such-path";
     params["log"] = "/no-such-path";
     auto store = make_ref<RestrictedStore>(params,
@@ -2322,7 +2345,7 @@ void DerivationGoal::startDaemon()
 }
 
 
-void DerivationGoal::stopDaemon()
+void LocalDerivationGoal::stopDaemon()
 {
     if (daemonSocket && shutdown(daemonSocket.get(), SHUT_RDWR) == -1)
         throw SysError("shutting down daemon socket");
@@ -2340,7 +2363,7 @@ void DerivationGoal::stopDaemon()
 }
 
 
-void DerivationGoal::addDependency(const StorePath & path)
+void LocalDerivationGoal::addDependency(const StorePath & path)
 {
     if (isAllowed(path)) return;
 
@@ -2397,8 +2420,7 @@ void DerivationGoal::addDependency(const StorePath & path)
     }
 }
 
-
-void DerivationGoal::chownToBuilder(const Path & path)
+void LocalDerivationGoal::chownToBuilder(const Path & path)
 {
     if (!buildUser) return;
     if (chown(path.c_str(), buildUser->getUID(), buildUser->getGID()) == -1)
@@ -2469,7 +2491,7 @@ void setupSeccomp()
 }
 
 
-void DerivationGoal::runChild()
+void LocalDerivationGoal::runChild()
 {
     /* Warning: in the child we should absolutely not make any SQLite
        calls! */
@@ -2977,7 +2999,7 @@ void DerivationGoal::runChild()
 }
 
 
-void DerivationGoal::registerOutputs()
+void LocalDerivationGoal::registerOutputs()
 {
     /* When using a build hook, the build hook can register the output
        as valid (by doing `nix-store --import').  If so we don't have
@@ -2987,14 +3009,8 @@ void DerivationGoal::registerOutputs()
        floating content-addressed derivations this isn't the case.
      */
     if (hook) {
-        bool allValid = true;
-        for (auto & [outputName, outputPath] : worker.store.queryPartialDerivationOutputMap(drvPath)) {
-            if (!outputPath || !worker.store.isValidPath(*outputPath))
-                allValid = false;
-            else
-                finalOutputs.insert_or_assign(outputName, *outputPath);
-        }
-        if (allValid) return;
+        DerivationGoal::registerOutputs();
+        return;
     }
 
     std::map<std::string, ValidPathInfo> infos;
@@ -3349,10 +3365,7 @@ void DerivationGoal::registerOutputs()
             }
         }
 
-        auto localStoreP = dynamic_cast<LocalStore *>(&worker.store);
-        if (!localStoreP)
-            throw Unsupported("can only register outputs with local store, but this is %s", worker.store.getUri());
-        auto & localStore = *localStoreP;
+        auto & localStore = getLocalStore();
 
         if (buildMode == bmCheck) {
 
@@ -3481,10 +3494,7 @@ void DerivationGoal::registerOutputs()
        paths referenced by each of them.  If there are cycles in the
        outputs, this will fail. */
     {
-        auto localStoreP = dynamic_cast<LocalStore *>(&worker.store);
-        if (!localStoreP)
-            throw Unsupported("can only register outputs with local store, but this is %s", worker.store.getUri());
-        auto & localStore = *localStoreP;
+        auto & localStore = getLocalStore();
 
         ValidPathInfos infos2;
         for (auto & [outputName, newInfo] : infos) {
@@ -3513,7 +3523,7 @@ void DerivationGoal::registerOutputs()
 }
 
 
-void DerivationGoal::checkOutputs(const std::map<Path, ValidPathInfo> & outputs)
+void LocalDerivationGoal::checkOutputs(const std::map<Path, ValidPathInfo> & outputs)
 {
     std::map<Path, const ValidPathInfo &> outputsByPath;
     for (auto & output : outputs)
@@ -3678,6 +3688,7 @@ void DerivationGoal::checkOutputs(const std::map<Path, ValidPathInfo> & outputs)
 }
 
 
+#if 0
 Path DerivationGoal::openLogFile()
 {
     logSize = 0;
@@ -3720,9 +3731,10 @@ void DerivationGoal::closeLogFile()
     logSink = logFileSink = 0;
     fdLogFile = -1;
 }
+#endif
 
 
-void DerivationGoal::deleteTmpDir(bool force)
+void LocalDerivationGoal::deleteTmpDir(bool force)
 {
     if (tmpDir != "") {
         /* Don't keep temporary directories for builtins because they
@@ -3738,10 +3750,17 @@ void DerivationGoal::deleteTmpDir(bool force)
 }
 
 
+bool LocalDerivationGoal::isReadDesc(int fd)
+{
+    return (hook && DerivationGoal::isReadDesc(fd)) ||
+        (!hook && fd == builderOut.readSide.get());
+}
+
+
+#if 0
 void DerivationGoal::handleChildOutput(int fd, const string & data)
 {
-    if ((hook && fd == hook->builderOut.readSide.get()) ||
-        (!hook && fd == builderOut.readSide.get()))
+    if (isReadDesc(fd))
     {
         logSize += data.size();
         if (settings.maxLogSize && logSize > settings.maxLogSize) {
@@ -3855,9 +3874,10 @@ void DerivationGoal::checkPathValidity()
         }
     }
 }
+#endif
 
 
-StorePath DerivationGoal::makeFallbackPath(std::string_view outputName)
+StorePath LocalDerivationGoal::makeFallbackPath(std::string_view outputName)
 {
     return worker.store.makeStorePath(
         "rewrite:" + std::string(drvPath.to_string()) + ":name:" + std::string(outputName),
@@ -3865,7 +3885,7 @@ StorePath DerivationGoal::makeFallbackPath(std::string_view outputName)
 }
 
 
-StorePath DerivationGoal::makeFallbackPath(const StorePath & path)
+StorePath LocalDerivationGoal::makeFallbackPath(const StorePath & path)
 {
     return worker.store.makeStorePath(
         "rewrite:" + std::string(drvPath.to_string()) + ":" + std::string(path.to_string()),
@@ -3873,6 +3893,7 @@ StorePath DerivationGoal::makeFallbackPath(const StorePath & path)
 }
 
 
+#if 0
 void DerivationGoal::done(BuildResult::Status status, std::optional<Error> ex)
 {
     result.status = status;
@@ -3897,6 +3918,7 @@ void DerivationGoal::done(BuildResult::Status status, std::optional<Error> ex)
 
     worker.updateProgress();
 }
+#endif
 
 
 }
diff --git a/src/libstore/build/local-derivation-goal.hh b/src/libstore/build/local-derivation-goal.hh
index 6dc164922..f7994113e 100644
--- a/src/libstore/build/local-derivation-goal.hh
+++ b/src/libstore/build/local-derivation-goal.hh
@@ -1,48 +1,15 @@
 #pragma once
 
-#include "parsed-derivations.hh"
-#include "lock.hh"
+#include "derivation-goal.hh"
 #include "local-store.hh"
-#include "goal.hh"
 
 namespace nix {
 
-using std::map;
-
-struct HookInstance;
-
-typedef enum {rpAccept, rpDecline, rpPostpone} HookReply;
-
-/* Unless we are repairing, we don't both to test validity and just assume it,
-   so the choices are `Absent` or `Valid`. */
-enum struct PathStatus {
-    Corrupt,
-    Absent,
-    Valid,
-};
-
-struct InitialOutputStatus {
-    StorePath path;
-    PathStatus status;
-    /* Valid in the store, and additionally non-corrupt if we are repairing */
-    bool isValid() const {
-        return status == PathStatus::Valid;
-    }
-    /* Merely present, allowed to be corrupt */
-    bool isPresent() const {
-        return status == PathStatus::Corrupt
-            || status == PathStatus::Valid;
-    }
-};
-
-struct InitialOutput {
-    bool wanted;
-    Hash outputHash;
-    std::optional<InitialOutputStatus> known;
-};
-
-struct DerivationGoal : public Goal
+struct LocalDerivationGoal : public DerivationGoal
 {
+    LocalStore & getLocalStore();
+
+#if 0
     /* Whether to use an on-disk .drv file. */
     bool useDerivation;
 
@@ -78,6 +45,7 @@ struct DerivationGoal : public Goal
     StorePathSet inputPaths;
 
     std::map<std::string, InitialOutput> initialOutputs;
+#endif
 
     /* User selected for running the builder. */
     std::unique_ptr<UserLock> buildUser;
@@ -91,6 +59,7 @@ struct DerivationGoal : public Goal
     /* The path of the temporary directory in the sandbox. */
     Path tmpDirInSandbox;
 
+#if 0
     /* File descriptor for the log file. */
     AutoCloseFD fdLogFile;
     std::shared_ptr<BufferedSink> logFileSink, logSink;
@@ -105,6 +74,7 @@ struct DerivationGoal : public Goal
     size_t currentLogLinePos = 0; // to handle carriage return
 
     std::string currentHookLine;
+#endif
 
     /* Pipe for the builder's standard output/error. */
     Pipe builderOut;
@@ -120,8 +90,10 @@ struct DerivationGoal : public Goal
        namespace. */
     bool usingUserNamespace = true;
 
+#if 0
     /* The build hook. */
     std::unique_ptr<HookInstance> hook;
+#endif
 
     /* Whether we're currently doing a chroot build. */
     bool useChroot = false;
@@ -131,14 +103,18 @@ struct DerivationGoal : public Goal
     /* RAII object to delete the chroot directory. */
     std::shared_ptr<AutoDelete> autoDelChroot;
 
+#if 0
     /* The sort of derivation we are building. */
     DerivationType derivationType;
+#endif
 
     /* Whether to run the build in a private network namespace. */
     bool privateNetwork = false;
 
+#if 0
     typedef void (DerivationGoal::*GoalState)();
     GoalState state;
+#endif
 
     /* Stuff we need to pass to initChild(). */
     struct ChrootPath {
@@ -179,6 +155,7 @@ struct DerivationGoal : public Goal
      */
     OutputPathMap scratchOutputs;
 
+#if 0
     /* The final output paths of the build.
 
        - For input-addressed derivations, always the precomputed paths
@@ -190,18 +167,21 @@ struct DerivationGoal : public Goal
     OutputPathMap finalOutputs;
 
     BuildMode buildMode;
+#endif
 
     /* If we're repairing without a chroot, there may be outputs that
        are valid but corrupt.  So we redirect these outputs to
        temporary paths. */
     StorePathSet redirectedBadOutputs;
 
+#if 0
     BuildResult result;
 
     /* The current round, if we're building multiple times. */
     size_t curRound = 1;
 
     size_t nrRounds;
+#endif
 
     /* Path registration info from the previous round, if we're
        building multiple times. Since this contains the hash, it
@@ -214,6 +194,7 @@ struct DerivationGoal : public Goal
 
     const static Path homeDir;
 
+#if 0
     std::unique_ptr<MaintainCount<uint64_t>> mcExpectedBuilds, mcRunningBuilds;
 
     std::unique_ptr<Activity> act;
@@ -225,6 +206,7 @@ struct DerivationGoal : public Goal
 
     /* The remote machine on which we're building. */
     std::string machineName;
+#endif
 
     /* The recursive Nix daemon socket. */
     AutoCloseFD daemonSocket;
@@ -249,17 +231,14 @@ struct DerivationGoal : public Goal
 
     friend struct RestrictedStore;
 
-    DerivationGoal(const StorePath & drvPath,
-        const StringSet & wantedOutputs, Worker & worker,
-        BuildMode buildMode = bmNormal);
-    DerivationGoal(const StorePath & drvPath, const BasicDerivation & drv,
-        const StringSet & wantedOutputs, Worker & worker,
-        BuildMode buildMode = bmNormal);
-    ~DerivationGoal();
+    using DerivationGoal::DerivationGoal;
+
+    virtual ~LocalDerivationGoal() override;
 
     /* Whether we need to perform hash rewriting if there are valid output paths. */
     bool needsHashRewrite();
 
+#if 0
     void timedOut(Error && ex) override;
 
     string key() override;
@@ -280,13 +259,16 @@ struct DerivationGoal : public Goal
     void closureRepaired();
     void inputsRealised();
     void tryToBuild();
-    void tryLocalBuild();
+#endif
+    void tryLocalBuild() override;
+#if 0
     void buildDone();
 
     void resolvedFinished();
 
     /* Is the build hook willing to perform the build? */
     HookReply tryBuildHook();
+#endif
 
     /* Start building a derivation. */
     void startBuilder();
@@ -311,27 +293,46 @@ struct DerivationGoal : public Goal
     /* Make a file owned by the builder. */
     void chownToBuilder(const Path & path);
 
+    int getChildStatus() override;
+
     /* Run the builder's process. */
     void runChild();
 
     /* Check that the derivation outputs all exist and register them
        as valid. */
-    void registerOutputs();
+    void registerOutputs() override;
 
     /* Check that an output meets the requirements specified by the
        'outputChecks' attribute (or the legacy
        '{allowed,disallowed}{References,Requisites}' attributes). */
     void checkOutputs(const std::map<std::string, ValidPathInfo> & outputs);
 
+#if 0
     /* Open a log file and a pipe to it. */
     Path openLogFile();
 
     /* Close the log file. */
     void closeLogFile();
+#endif
+
+    /* Close the read side of the logger pipe. */
+    void closeReadPipes() override;
+
+    /* Cleanup hooks for buildDone() */
+    void cleanupHookFinally() override;
+    void cleanupPreChildKill() override;
+    void cleanupPostChildKill() override;
+    bool cleanupDecideWhetherDiskFull() override;
+    void cleanupPostOutputsRegisteredModeCheck() override;
+    void cleanupPostOutputsRegisteredModeNonCheck() override;
+
+    bool isReadDesc(int fd) override;
+
 
     /* Delete the temporary directory, if we have one. */
     void deleteTmpDir(bool force);
 
+#if 0
     /* Callback used by the worker to write to the log. */
     void handleChildOutput(int fd, const string & data) override;
     void handleEOF(int fd) override;
@@ -345,9 +346,10 @@ struct DerivationGoal : public Goal
 
     /* Return the set of (in)valid paths. */
     void checkPathValidity();
+#endif
 
     /* Forcibly kill the child process, if any. */
-    void killChild();
+    void killChild() override;
 
     /* Create alternative path calculated from but distinct from the
        input, so we can avoid overwriting outputs (or other store paths)
@@ -359,6 +361,7 @@ struct DerivationGoal : public Goal
        rewrites caught everything */
     StorePath makeFallbackPath(std::string_view outputName);
 
+#if 0
     void repairClosure();
 
     void started();
@@ -368,6 +371,7 @@ struct DerivationGoal : public Goal
         std::optional<Error> ex = {});
 
     StorePathSet exportReferences(const StorePathSet & storePaths);
+#endif
 };
 
 }
diff --git a/src/libstore/build/worker.cc b/src/libstore/build/worker.cc
index 2f13aa885..b2223c3b6 100644
--- a/src/libstore/build/worker.cc
+++ b/src/libstore/build/worker.cc
@@ -1,7 +1,7 @@
 #include "machines.hh"
 #include "worker.hh"
 #include "substitution-goal.hh"
-#include "derivation-goal.hh"
+#include "local-derivation-goal.hh"
 #include "hook-instance.hh"
 
 #include <poll.h>
@@ -59,8 +59,10 @@ std::shared_ptr<DerivationGoal> Worker::makeDerivationGoalCommon(
 std::shared_ptr<DerivationGoal> Worker::makeDerivationGoal(const StorePath & drvPath,
     const StringSet & wantedOutputs, BuildMode buildMode)
 {
-    return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() {
-        return std::make_shared<DerivationGoal>(drvPath, wantedOutputs, *this, buildMode);
+    return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() -> std::shared_ptr<DerivationGoal> {
+        return !dynamic_cast<LocalStore *>(&store)
+            ? std::make_shared</* */DerivationGoal>(drvPath, wantedOutputs, *this, buildMode)
+            : std::make_shared<LocalDerivationGoal>(drvPath, wantedOutputs, *this, buildMode);
     });
 }
 
@@ -68,8 +70,10 @@ std::shared_ptr<DerivationGoal> Worker::makeDerivationGoal(const StorePath & drv
 std::shared_ptr<DerivationGoal> Worker::makeBasicDerivationGoal(const StorePath & drvPath,
     const BasicDerivation & drv, const StringSet & wantedOutputs, BuildMode buildMode)
 {
-    return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() {
-        return std::make_shared<DerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode);
+    return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() -> std::shared_ptr<DerivationGoal> {
+        return !dynamic_cast<LocalStore *>(&store)
+            ? std::make_shared</* */DerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode)
+            : std::make_shared<LocalDerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode);
     });
 }
 
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 780cc0f07..03bb0218d 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -280,7 +280,7 @@ private:
 
     void createUser(const std::string & userName, uid_t userId) override;
 
-    friend struct DerivationGoal;
+    friend struct LocalDerivationGoal;
     friend struct SubstitutionGoal;
 };