Merge branch 'small-storePath-cleanups' into path-info

52 files changed, 475 insertions, 194 deletions

diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
index a268d7caf..344f9405f 100644
--- a/.github/PULL_REQUEST_TEMPLATE.md
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -21,7 +21,7 @@ Maintainers: tick if completed or explain if not relevant
  - [ ] tests, as appropriate
    - functional tests - `tests/**.sh`
    - unit tests - `src/*/tests`
-   - integration tests
+   - integration tests - `tests/nixos/*`
  - [ ] documentation in the manual
  - [ ] code and comments are self-explanatory
  - [ ] commit message explains why the change was made
diff --git a/.github/workflows/backport.yml b/.github/workflows/backport.yml
index 9f8d14509..ca5af260f 100644
--- a/.github/workflows/backport.yml
+++ b/.github/workflows/backport.yml
@@ -21,7 +21,7 @@ jobs:
           fetch-depth: 0
       - name: Create backport PRs
         # should be kept in sync with `version`
-        uses: zeebe-io/backport-action@v1.0.1
+        uses: zeebe-io/backport-action@v1.1.0
         with:
           # Config README: https://github.com/zeebe-io/backport-action#backport-action
           github_token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/boehmgc-coroutine-sp-fallback.diff b/boehmgc-coroutine-sp-fallback.diff
new file mode 100644
index 000000000..2826486fb
--- /dev/null
+++ b/boehmgc-coroutine-sp-fallback.diff
@@ -0,0 +1,77 @@
+diff --git a/darwin_stop_world.c b/darwin_stop_world.c
+index 3dbaa3fb..36a1d1f7 100644
+--- a/darwin_stop_world.c
++++ b/darwin_stop_world.c
+@@ -352,6 +352,7 @@ GC_INNER void GC_push_all_stacks(void)
+   int nthreads = 0;
+   word total_size = 0;
+   mach_msg_type_number_t listcount = (mach_msg_type_number_t)THREAD_TABLE_SZ;
++  size_t stack_limit;
+   if (!EXPECT(GC_thr_initialized, TRUE))
+     GC_thr_init();
+ 
+@@ -407,6 +408,19 @@ GC_INNER void GC_push_all_stacks(void)
+             GC_push_all_stack_sections(lo, hi, p->traced_stack_sect);
+           }
+           if (altstack_lo) {
++            // When a thread goes into a coroutine, we lose its original sp until
++            // control flow returns to the thread.
++            // While in the coroutine, the sp points outside the thread stack,
++            // so we can detect this and push the entire thread stack instead,
++            // as an approximation.
++            // We assume that the coroutine has similarly added its entire stack.
++            // This could be made accurate by cooperating with the application
++            // via new functions and/or callbacks.
++            stack_limit = pthread_get_stacksize_np(p->id);
++            if (altstack_lo >= altstack_hi || altstack_lo < altstack_hi - stack_limit) { // sp outside stack
++              altstack_lo = altstack_hi - stack_limit;
++            }
++
+             total_size += altstack_hi - altstack_lo;
+             GC_push_all_stack(altstack_lo, altstack_hi);
+           }
+diff --git a/pthread_stop_world.c b/pthread_stop_world.c
+index b5d71e62..aed7b0bf 100644
+--- a/pthread_stop_world.c
++++ b/pthread_stop_world.c
+@@ -768,6 +768,8 @@ STATIC void GC_restart_handler(int sig)
+ /* world is stopped.  Should not fail if it isn't.                      */
+ GC_INNER void GC_push_all_stacks(void)
+ {
++    size_t stack_limit;
++    pthread_attr_t pattr;
+     GC_bool found_me = FALSE;
+     size_t nthreads = 0;
+     int i;
+@@ -851,6 +853,31 @@ GC_INNER void GC_push_all_stacks(void)
+           hi = p->altstack + p->altstack_size;
+           /* FIXME: Need to scan the normal stack too, but how ? */
+           /* FIXME: Assume stack grows down */
++        } else {
++          if (pthread_getattr_np(p->id, &pattr)) {
++            ABORT("GC_push_all_stacks: pthread_getattr_np failed!");
++          }
++          if (pthread_attr_getstacksize(&pattr, &stack_limit)) {
++            ABORT("GC_push_all_stacks: pthread_attr_getstacksize failed!");
++          }
++          if (pthread_attr_destroy(&pattr)) {
++            ABORT("GC_push_all_stacks: pthread_attr_destroy failed!");
++          }
++          // When a thread goes into a coroutine, we lose its original sp until
++          // control flow returns to the thread.
++          // While in the coroutine, the sp points outside the thread stack,
++          // so we can detect this and push the entire thread stack instead,
++          // as an approximation.
++          // We assume that the coroutine has similarly added its entire stack.
++          // This could be made accurate by cooperating with the application
++          // via new functions and/or callbacks.
++          #ifndef STACK_GROWS_UP
++            if (lo >= hi || lo < hi - stack_limit) { // sp outside stack
++              lo = hi - stack_limit;
++            }
++          #else
++          #error "STACK_GROWS_UP not supported in boost_coroutine2 (as of june 2021), so we don't support it in Nix."
++          #endif
+         }
+         GC_push_all_stack_sections(lo, hi, traced_stack_sect);
+ #       ifdef STACK_GROWS_UP
diff --git a/doc/manual/src/command-ref/nix-store.md b/doc/manual/src/command-ref/nix-store.md
index f6017481c..403cf285d 100644
--- a/doc/manual/src/command-ref/nix-store.md
+++ b/doc/manual/src/command-ref/nix-store.md
@@ -82,8 +82,8 @@ paths. Realisation is a somewhat overloaded term:
     produced through substitutes. If there are no (successful)
     substitutes, realisation fails.
 
-[valid]: ../glossary.md#validity
-[substitutes]: ../glossary.md#substitute
+[valid]: ../glossary.md#gloss-validity
+[substitutes]: ../glossary.md#gloss-substitute
 
 The output path of each derivation is printed on standard output. (For
 non-derivations argument, the argument itself is printed.)
diff --git a/doc/manual/src/glossary.md b/doc/manual/src/glossary.md
index 5a49af8dc..6004df833 100644
--- a/doc/manual/src/glossary.md
+++ b/doc/manual/src/glossary.md
@@ -156,6 +156,8 @@
     to path `Q`, then `Q` is in the closure of `P`. Further, if `Q`
     references `R` then `R` is also in the closure of `P`.
 
+    [closure]: #gloss-closure
+
   - [output path]{#gloss-output-path}\
     A [store path] produced by a [derivation].
 
@@ -172,6 +174,8 @@
     - The store path is listed in the Nix database as being valid.
     - All paths in the store path's [closure] are valid.
 
+    [validity]: #gloss-validity
+
   - [user environment]{#gloss-user-env}\
     An automatically generated store object that consists of a set of
     symlinks to “active” applications, i.e., other store paths. These
diff --git a/doc/manual/src/language/advanced-attributes.md b/doc/manual/src/language/advanced-attributes.md
index 2e7e80ed0..f02425b13 100644
--- a/doc/manual/src/language/advanced-attributes.md
+++ b/doc/manual/src/language/advanced-attributes.md
@@ -207,13 +207,13 @@ Derivations can declare some infrequently used optional attributes.
     the hash in either hexadecimal or base-32 notation. (See the
     [`nix-hash` command](../command-ref/nix-hash.md) for information
     about converting to and from base-32 notation.)
-    
+
   - [`__contentAddressed`]{#adv-attr-__contentAddressed}
     If this **experimental** attribute is set to true, then the derivation
     outputs will be stored in a content-addressed location rather than the
     traditional input-addressed one.
-    This only has an effect if the `ca-derivation` experimental feature is enabled.
-    
+    This only has an effect if the `ca-derivations` experimental feature is enabled.
+
     Setting this attribute also requires setting `outputHashMode` and `outputHashAlgo` like for *fixed-output derivations* (see above).
 
   - [`passAsFile`]{#adv-attr-passAsFile}\
diff --git a/doc/manual/src/release-notes/rl-2.13.md b/doc/manual/src/release-notes/rl-2.13.md
index 2ebf19f60..168708113 100644
--- a/doc/manual/src/release-notes/rl-2.13.md
+++ b/doc/manual/src/release-notes/rl-2.13.md
@@ -25,11 +25,11 @@
 * Allow explicitly selecting outputs in a store derivation installable, just like we can do with other sorts of installables.
   For example,
   ```shell-session
-  # nix-build /nix/store/gzaflydcr6sb3567hap9q6srzx8ggdgg-glibc-2.33-78.drv^dev
+  # nix build /nix/store/gzaflydcr6sb3567hap9q6srzx8ggdgg-glibc-2.33-78.drv^dev
   ```
   now works just as
   ```shell-session
-  # nix-build glibc^dev
+  # nix build nixpkgs#glibc^dev
   ```
   does already.
 
diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md
index 8a79703ab..7e8344e63 100644
--- a/doc/manual/src/release-notes/rl-next.md
+++ b/doc/manual/src/release-notes/rl-next.md
@@ -8,3 +8,15 @@
   discovered by making multiple syscalls. This change makes these operations
   lazy such that these lookups will only be performed if the attribute is used.
   This optimization affects a minority of filesystems and operating systems.
+
+* In derivations that use structured attributes, you can now use `unsafeDiscardReferences`
+  to disable scanning a given output for runtime dependencies:
+  ```nix
+  __structuredAttrs = true;
+  unsafeDiscardReferences.out = true;
+  ```
+  This is useful e.g. when generating self-contained filesystem images with
+  their own embedded Nix store: hashes found inside such an image refer
+  to the embedded store and not to the host's Nix store.
+
+  This requires the `discard-references` experimental feature.
diff --git a/flake.nix b/flake.nix
index 5796c54ea..0325f33b1 100644
--- a/flake.nix
+++ b/flake.nix
@@ -131,9 +131,14 @@
           });
 
         propagatedDeps =
-          [ (boehmgc.override {
+          [ ((boehmgc.override {
               enableLargeConfig = true;
+            }).overrideAttrs(o: {
+              patches = (o.patches or []) ++ [
+                ./boehmgc-coroutine-sp-fallback.diff
+              ];
             })
+            )
             nlohmann_json
           ];
       };
@@ -404,6 +409,18 @@
           };
         };
 
+      nixos-lib = import (nixpkgs + "/nixos/lib") { };
+
+      # https://nixos.org/manual/nixos/unstable/index.html#sec-calling-nixos-tests
+      runNixOSTestFor = system: test: nixos-lib.runTest {
+        imports = [ test ];
+        hostPkgs = nixpkgsFor.${system};
+        defaults = {
+          nixpkgs.pkgs = nixpkgsFor.${system};
+        };
+        _module.args.nixpkgs = nixpkgs;
+      };
+
     in {
 
       # A Nixpkgs overlay that overrides the 'nix' and
@@ -460,6 +477,10 @@
 
             src = self;
 
+            configureFlags = [
+              "CXXFLAGS=-I${lib.getDev pkgs.rapidcheck}/extras/gtest/include"
+            ];
+
             enableParallelBuilding = true;
 
             nativeBuildInputs = nativeBuildDeps;
@@ -478,49 +499,22 @@
           };
 
         # System tests.
-        tests.remoteBuilds = import ./tests/remote-builds.nix {
-          system = "x86_64-linux";
-          inherit nixpkgs;
-          overlay = self.overlays.default;
-        };
+        tests.remoteBuilds = runNixOSTestFor "x86_64-linux" ./tests/nixos/remote-builds.nix;
 
-        tests.nix-copy-closure = import ./tests/nix-copy-closure.nix {
-          system = "x86_64-linux";
-          inherit nixpkgs;
-          overlay = self.overlays.default;
-        };
+        tests.nix-copy-closure = runNixOSTestFor "x86_64-linux" ./tests/nixos/nix-copy-closure.nix;
 
-        tests.nssPreload = (import ./tests/nss-preload.nix rec {
-          system = "x86_64-linux";
-          inherit nixpkgs;
-          overlay = self.overlays.default;
-        });
+        tests.nssPreload = runNixOSTestFor "x86_64-linux" ./tests/nixos/nss-preload.nix;
 
-        tests.githubFlakes = (import ./tests/github-flakes.nix rec {
-          system = "x86_64-linux";
-          inherit nixpkgs;
-          overlay = self.overlays.default;
-        });
+        tests.githubFlakes = runNixOSTestFor "x86_64-linux" ./tests/nixos/github-flakes.nix;
 
-        tests.sourcehutFlakes = (import ./tests/sourcehut-flakes.nix rec {
-          system = "x86_64-linux";
-          inherit nixpkgs;
-          overlay = self.overlays.default;
-        });
+        tests.sourcehutFlakes = runNixOSTestFor "x86_64-linux" ./tests/nixos/sourcehut-flakes.nix;
 
-        tests.containers = (import ./tests/containers.nix rec {
-          system = "x86_64-linux";
-          inherit nixpkgs;
-          overlay = self.overlays.default;
-        });
+        tests.containers = runNixOSTestFor "x86_64-linux" ./tests/nixos/containers/containers.nix;
 
         tests.setuid = nixpkgs.lib.genAttrs
           ["i686-linux" "x86_64-linux"]
-          (system:
-            import ./tests/setuid.nix rec {
-              inherit nixpkgs system;
-              overlay = self.overlays.default;
-            });
+          (system: runNixOSTestFor system ./tests/nixos/setuid.nix);
+
 
         # Make sure that nix-env still produces the exact same result
         # on a particular version of Nixpkgs.
@@ -653,6 +647,7 @@
             inherit system crossSystem;
             overlays = [ self.overlays.default ];
           };
+          inherit (nixpkgsCross) lib;
         in with commonDeps { pkgs = nixpkgsCross; }; nixpkgsCross.stdenv.mkDerivation {
           name = "nix-${version}";
 
@@ -665,7 +660,11 @@
           nativeBuildInputs = nativeBuildDeps;
           buildInputs = buildDeps ++ propagatedDeps;
 
-          configureFlags = [ "--sysconfdir=/etc" "--disable-doc-gen" ];
+          configureFlags = [
+            "CXXFLAGS=-I${lib.getDev nixpkgsCross.rapidcheck}/extras/gtest/include"
+            "--sysconfdir=/etc"
+            "--disable-doc-gen"
+          ];
 
           enableParallelBuilding = true;
 
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 1828b8c2e..a48968656 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -519,6 +519,7 @@ EvalState::EvalState(
     static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
 
     /* Initialise the Nix expression search path. */
+    evalSettings.nixPath.setDefault(evalSettings.getDefaultNixPath());
     if (!evalSettings.pureEval) {
         for (auto & i : _searchPath) addToSearchPath(i);
         for (auto & i : evalSettings.nixPath.get()) addToSearchPath(i);
@@ -2472,30 +2473,35 @@ std::ostream & operator << (std::ostream & str, const ExternalValueBase & v) {
 
 EvalSettings::EvalSettings()
 {
-    auto var = getEnv("NIX_PATH");
-    if (var) nixPath = parseNixPath(*var);
 }
 
+/* impure => NIX_PATH or a default path
+ * restrict-eval => NIX_PATH
+ * pure-eval => empty
+ */
 Strings EvalSettings::getDefaultNixPath()
 {
-    Strings res;
-    auto add = [&](const Path & p, const std::string & s = std::string()) {
-        if (pathExists(p)) {
-            if (s.empty()) {
-                res.push_back(p);
-            } else {
-                res.push_back(s + "=" + p);
-            }
-        }
-    };
+    if (pureEval)
+        return {};
+
+    auto var = getEnv("NIX_PATH");
+    if (var) {
+        return parseNixPath(*var);
+    } else if (restrictEval) {
+        return {};
+    } else {
+        Strings res;
+        auto add = [&](const Path & p, const std::optional<std::string> & s = std::nullopt) {
+            if (pathExists(p))
+                res.push_back(s ? *s + "=" + p : p);
+        };
 
-    if (!evalSettings.restrictEval && !evalSettings.pureEval) {
         add(getHome() + "/.nix-defexpr/channels");
         add(settings.nixStateDir + "/profiles/per-user/root/channels/nixpkgs", "nixpkgs");
         add(settings.nixStateDir + "/profiles/per-user/root/channels");
-    }
 
-    return res;
+        return res;
+    }
 }
 
 bool EvalSettings::isPseudoUrl(std::string_view s)
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index e4d5906bd..2340ef67b 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -570,7 +570,7 @@ struct EvalSettings : Config
 {
     EvalSettings();
 
-    static Strings getDefaultNixPath();
+    Strings getDefaultNixPath();
 
     static bool isPseudoUrl(std::string_view s);
 
@@ -580,8 +580,15 @@ struct EvalSettings : Config
         "Whether builtin functions that allow executing native code should be enabled."};
 
     Setting<Strings> nixPath{
-        this, getDefaultNixPath(), "nix-path",
-        "List of directories to be searched for `<...>` file references."};
+        this, {}, "nix-path",
+        R"(
+          List of directories to be searched for `<...>` file references.
+
+          If [pure evaluation](#conf-pure-eval) is disabled,
+          this is initialised using the [`NIX_PATH`](@docroot@/command-ref/env-common.md#env-NIX_PATH)
+          environment variable, or, if it is unset and [restricted evaluation](#conf-restrict-eval)
+          is disabled, a default search path including the user's and `root`'s channels.
+        )"};
 
     Setting<bool> restrictEval{
         this, false, "restrict-eval",
diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 98f8cb061..8fdc9dce1 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -1517,7 +1517,7 @@ void LocalDerivationGoal::startDaemon()
                 try {
                     daemon::processConnection(store, from, to,
                         daemon::NotTrusted, daemon::Recursive,
-                        [&](Store & store) { store.createUser("nobody", 65535); });
+                        [&](Store & store) {});
                     debug("terminated daemon connection");
                 } catch (SysError &) {
                     ignoreException();
@@ -2323,11 +2323,28 @@ DrvOutputs LocalDerivationGoal::registerOutputs()
             buildUser ? std::optional(buildUser->getUIDRange()) : std::nullopt,
             inodesSeen);
 
-        debug("scanning for references for output '%s' in temp location '%s'", outputName, actualPath);
+        bool discardReferences = false;
+        if (auto structuredAttrs = parsedDrv->getStructuredAttrs()) {
+            if (auto udr = get(*structuredAttrs, "unsafeDiscardReferences")) {
+                settings.requireExperimentalFeature(Xp::DiscardReferences);
+                if (auto output = get(*udr, outputName)) {
+                    if (!output->is_boolean())
+                        throw Error("attribute 'unsafeDiscardReferences.\"%s\"' of derivation '%s' must be a Boolean", outputName, drvPath.to_string());
+                    discardReferences = output->get<bool>();
+                }
+            }
+        }
 
-        /* Pass blank Sink as we are not ready to hash data at this stage. */
-        NullSink blank;
-        auto references = scanForReferences(blank, actualPath, referenceablePaths);
+        StorePathSet references;
+        if (discardReferences)
+            debug("discarding references of output '%s'", outputName);
+        else {
+            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;
+            references = scanForReferences(blank, actualPath, referenceablePaths);
+        }
 
         outputReferencesIfUnregistered.insert_or_assign(
             outputName,
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index 12596ba49..e2a7dab35 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -222,7 +222,8 @@ struct ClientSettings
                     else if (!hasSuffix(s, "/") && trusted.count(s + "/"))
                         subs.push_back(s + "/");
                     else
-                        warn("ignoring untrusted substituter '%s'", s);
+                        warn("ignoring untrusted substituter '%s', you are not a trusted user.\n"
+                             "Run `man nix.conf` for more information on the `substituters` configuration option.", s);
                 res = subs;
                 return true;
             };
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index 7111def92..c3ccb5e11 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -570,11 +570,15 @@ public:
         {"cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="},
         "trusted-public-keys",
         R"(
-          A whitespace-separated list of public keys. When paths are copied
-          from another Nix store (such as a binary cache), they must be
-          signed with one of these keys. For example:
-          `cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
-          hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=`.
+          A whitespace-separated list of public keys.
+
+          At least one of the following condition must be met
+          for Nix to accept copying a store object from another
+          Nix store (such as a substituter):
+
+          - the store object has been signed using a key in the trusted keys list
+          - the [`require-sigs`](#conf-require-sigs) option has been set to `false`
+          - the store object is [output-addressed](@docroot@/glossary.md#gloss-output-addressed-store-object)
         )",
         {"binary-cache-public-keys"}};
 
@@ -670,13 +674,14 @@ public:
           independently. Lower value means higher priority.
           The default is `https://cache.nixos.org`, with a Priority of 40.
 
-          Nix will copy a store path from a remote store only if one
-          of the following is true:
+          At least one of the following conditions must be met for Nix to use
+          a substituter:
 
-          - the store object is signed by one of the [`trusted-public-keys`](#conf-trusted-public-keys)
           - the substituter is in the [`trusted-substituters`](#conf-trusted-substituters) list
-          - the [`require-sigs`](#conf-require-sigs) option has been set to `false`
-          - the store object is [output-addressed](@docroot@/glossary.md#gloss-output-addressed-store-object)
+          - the user calling Nix is in the [`trusted-users`](#conf-trusted-users) list
+
+          In addition, each store path should be trusted as described
+          in [`trusted-public-keys`](#conf-trusted-public-keys)
         )",
         {"binary-caches"}};
 
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index e55ccab84..c6f870dde 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -201,8 +201,6 @@ LocalStore::LocalStore(const Params & params)
             throw SysError("could not set permissions on '%s' to 755", perUserDir);
     }
 
-    createUser(getUserName(), getuid());
-
     /* Optionally, create directories and set permissions for a
        multi-user install. */
     if (getuid() == 0 && settings.buildUsersGroup != "") {
@@ -1844,20 +1842,6 @@ void LocalStore::signPathInfo(ValidPathInfo & info)
 }
 
 
-void LocalStore::createUser(const std::string & userName, uid_t userId)
-{
-    for (auto & dir : {
-        fmt("%s/profiles/per-user/%s", stateDir, userName),
-        fmt("%s/gcroots/per-user/%s", stateDir, userName)
-    }) {
-        createDirs(dir);
-        if (chmod(dir.c_str(), 0755) == -1)
-            throw SysError("changing permissions of directory '%s'", dir);
-        if (chown(dir.c_str(), userId, getgid()) == -1)
-            throw SysError("changing owner of directory '%s'", dir);
-    }
-}
-
 std::optional<std::pair<int64_t, Realisation>> LocalStore::queryRealisationCore_(
         LocalStore::State & state,
         const DrvOutput & id)
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 06d36a7d5..a84eb7c26 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -281,8 +281,6 @@ private:
     void signPathInfo(ValidPathInfo & info);
     void signRealisation(Realisation &);
 
-    void createUser(const std::string & userName, uid_t userId) override;
-
     // XXX: Make a generic `Store` method
     FixedOutputHash hashCAPath(
         const FileIngestionMethod & method,
diff --git a/src/libstore/profiles.cc b/src/libstore/profiles.cc
index 3e4188188..b202351ce 100644
--- a/src/libstore/profiles.cc
+++ b/src/libstore/profiles.cc
@@ -280,16 +280,24 @@ std::string optimisticLockProfile(const Path & profile)
 }
 
 
+Path profilesDir()
+{
+    auto profileRoot = getDataDir() + "/nix/profiles";
+    createDirs(profileRoot);
+    return profileRoot;
+}
+
+
 Path getDefaultProfile()
 {
     Path profileLink = getHome() + "/.nix-profile";
     try {
+        auto profile =
+            getuid() == 0
+            ? settings.nixStateDir + "/profiles/default"
+            : profilesDir() + "/profile";
         if (!pathExists(profileLink)) {
-            replaceSymlink(
-                getuid() == 0
-                ? settings.nixStateDir + "/profiles/default"
-                : fmt("%s/profiles/per-user/%s/profile", settings.nixStateDir, getUserName()),
-                profileLink);
+            replaceSymlink(profile, profileLink);
         }
         return absPath(readLink(profileLink), dirOf(profileLink));
     } catch (Error &) {
diff --git a/src/libstore/profiles.hh b/src/libstore/profiles.hh
index 408ca039c..73667a798 100644
--- a/src/libstore/profiles.hh
+++ b/src/libstore/profiles.hh
@@ -68,6 +68,10 @@ void lockProfile(PathLocks & lock, const Path & profile);
    rebuilt. */
 std::string optimisticLockProfile(const Path & profile);
 
+/* Creates and returns the path to a directory suitable for storing the user’s
+   profiles. */
+Path profilesDir();
+
 /* Resolve ~/.nix-profile. If ~/.nix-profile doesn't exist yet, create
    it. */
 Path getDefaultProfile();
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 2d252db84..72517c6e4 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -653,9 +653,6 @@ public:
         return toRealPath(printStorePath(storePath));
     }
 
-    virtual void createUser(const std::string & userName, uid_t userId)
-    { }
-
     /*
      * Synchronises the options of the client with those of the daemon
      * (a no-op when there’s no daemon)
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index 7d236028c..0ebeaba61 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -74,6 +74,8 @@ struct AbstractPos
     virtual void print(std::ostream & out) const = 0;
 
     std::optional<LinesOfCode> getCodeLines() const;
+
+    virtual ~AbstractPos() = default;
 };
 
 std::ostream & operator << (std::ostream & str, const AbstractPos & pos);
diff --git a/src/libutil/experimental-features.cc b/src/libutil/experimental-features.cc
index e0902971e..58d762ebb 100644
--- a/src/libutil/experimental-features.cc
+++ b/src/libutil/experimental-features.cc
@@ -16,6 +16,7 @@ std::map<ExperimentalFeature, std::string> stringifiedXpFeatures = {
     { Xp::ReplFlake, "repl-flake" },
     { Xp::AutoAllocateUids, "auto-allocate-uids" },
     { Xp::Cgroups, "cgroups" },
+    { Xp::DiscardReferences, "discard-references" },
 };
 
 const std::optional<ExperimentalFeature> parseExperimentalFeature(const std::string_view & name)
diff --git a/src/libutil/experimental-features.hh b/src/libutil/experimental-features.hh
index af775feb0..ac372e03e 100644
--- a/src/libutil/experimental-features.hh
+++ b/src/libutil/experimental-features.hh
@@ -25,6 +25,7 @@ enum struct ExperimentalFeature
     ReplFlake,
     AutoAllocateUids,
     Cgroups,
+    DiscardReferences,
 };
 
 /**
diff --git a/src/libutil/tests/url.cc b/src/libutil/tests/url.cc
index c3b233797..e0c438b4d 100644
--- a/src/libutil/tests/url.cc
+++ b/src/libutil/tests/url.cc
@@ -99,6 +99,27 @@ namespace nix {
         ASSERT_EQ(parsed, expected);
     }
 
+    TEST(parseURL, parsesFilePlusHttpsUrl) {
+        auto s = "file+https://www.example.org/video.mp4";
+        auto parsed = parseURL(s);
+
+        ParsedURL expected {
+            .url = "file+https://www.example.org/video.mp4",
+            .base = "https://www.example.org/video.mp4",
+            .scheme = "file+https",
+            .authority = "www.example.org",
+            .path = "/video.mp4",
+            .query = (StringMap) { },
+            .fragment = "",
+        };
+
+        ASSERT_EQ(parsed, expected);
+    }
+
+    TEST(parseURL, rejectsAuthorityInUrlsWithFileTransportation) {
+        auto s = "file://www.example.org/video.mp4";
+        ASSERT_THROW(parseURL(s), Error);
+    }
 
     TEST(parseURL, parseIPv4Address) {
         auto s = "http://127.0.0.1:8080/file.tar.gz?download=fast&when=now#hello";
diff --git a/src/libutil/url.cc b/src/libutil/url.cc
index 5b7abeb49..4e43455e1 100644
--- a/src/libutil/url.cc
+++ b/src/libutil/url.cc
@@ -30,13 +30,13 @@ ParsedURL parseURL(const std::string & url)
         auto & query = match[6];
         auto & fragment = match[7];
 
-        auto isFile = scheme.find("file") != std::string::npos;
+        auto transportIsFile = parseUrlScheme(scheme).transport == "file";
 
-        if (authority && *authority != "" && isFile)
+        if (authority && *authority != "" && transportIsFile)
             throw BadURL("file:// URL '%s' has unexpected authority '%s'",
                 url, *authority);
 
-        if (isFile && path.empty())
+        if (transportIsFile && path.empty())
             path = "/";
 
         return ParsedURL{
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 993dc1cb6..40faa4bf2 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -537,6 +537,16 @@ std::string getUserName()
     return name;
 }
 
+Path getHomeOf(uid_t userId)
+{
+    std::vector<char> buf(16384);
+    struct passwd pwbuf;
+    struct passwd * pw;
+    if (getpwuid_r(userId, &pwbuf, buf.data(), buf.size(), &pw) != 0
+        || !pw || !pw->pw_dir || !pw->pw_dir[0])
+        throw Error("cannot determine user's home directory");
+    return pw->pw_dir;
+}
 
 Path getHome()
 {
@@ -558,13 +568,7 @@ Path getHome()
             }
         }
         if (!homeDir) {
-            std::vector<char> buf(16384);
-            struct passwd pwbuf;
-            struct passwd * pw;
-            if (getpwuid_r(geteuid(), &pwbuf, buf.data(), buf.size(), &pw) != 0
-                || !pw || !pw->pw_dir || !pw->pw_dir[0])
-                throw Error("cannot determine user's home directory");
-            homeDir = pw->pw_dir;
+            homeDir = getHomeOf(geteuid());
             if (unownedUserHomeDir.has_value() && unownedUserHomeDir != homeDir) {
                 warn("$HOME ('%s') is not owned by you, falling back to the one defined in the 'passwd' file ('%s')", *unownedUserHomeDir, *homeDir);
             }
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 9b149de80..266da0ae3 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -137,6 +137,9 @@ void deletePath(const Path & path, uint64_t & bytesFreed);
 
 std::string getUserName();
 
+/* Return the given user's home directory from /etc/passwd. */
+Path getHomeOf(uid_t userId);
+
 /* Return $HOME or the user's home directory from /etc/passwd. */
 Path getHome();
 
diff --git a/src/nix-channel/nix-channel.cc b/src/nix-channel/nix-channel.cc
index cf52b03b4..263d85eea 100755
--- a/src/nix-channel/nix-channel.cc
+++ b/src/nix-channel/nix-channel.cc
@@ -1,9 +1,11 @@
+#include "profiles.hh"
 #include "shared.hh"
 #include "globals.hh"
 #include "filetransfer.hh"
 #include "store-api.hh"
 #include "legacy.hh"
 #include "fetchers.hh"
+#include "util.hh"
 
 #include <fcntl.h>
 #include <regex>
@@ -166,7 +168,7 @@ static int main_nix_channel(int argc, char ** argv)
         nixDefExpr = home + "/.nix-defexpr";
 
         // Figure out the name of the channels profile.
-        profile = fmt("%s/profiles/per-user/%s/channels", settings.nixStateDir, getUserName());
+        profile = profilesDir() + "/channels";
 
         enum {
             cNone,
diff --git a/src/nix/daemon.cc b/src/nix/daemon.cc
index c527fdb0a..19fbbf155 100644
--- a/src/nix/daemon.cc
+++ b/src/nix/daemon.cc
@@ -248,7 +248,6 @@ static void daemonLoop()
                         querySetting("build-users-group", "") == "")
                         throw Error("if you run 'nix-daemon' as root, then you MUST set 'build-users-group'!");
 #endif
-                    store.createUser(user, peer.uid);
                 });
 
                 exit(0);
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 020c1b182..d2f68c37c 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -966,6 +966,7 @@ struct CmdFlakeArchive : FlakeCommand, MixJSON, MixDryRun
 struct CmdFlakeShow : FlakeCommand, MixJSON
 {
     bool showLegacy = false;
+    bool showAllSystems = false;
 
     CmdFlakeShow()
     {
@@ -974,6 +975,11 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
             .description = "Show the contents of the `legacyPackages` output.",
             .handler = {&showLegacy, true}
         });
+        addFlag({
+            .longName = "all-systems",
+            .description = "Show the contents of outputs for all systems.",
+            .handler = {&showAllSystems, true}
+        });
     }
 
     std::string description() override
@@ -994,6 +1000,7 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
 
         auto state = getEvalState();
         auto flake = std::make_shared<LockedFlake>(lockFlake());
+        auto localSystem = std::string(settings.thisSystem.get());
 
         std::function<nlohmann::json(
             eval_cache::AttrCursor & visitor,
@@ -1084,10 +1091,18 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                     || (attrPath.size() == 3 && (attrPathS[0] == "checks" || attrPathS[0] == "packages" || attrPathS[0] == "devShells"))
                     )
                 {
-                    if (visitor.isDerivation())
-                        showDerivation();
-                    else
-                        throw Error("expected a derivation");
+                    if (!showAllSystems && std::string(attrPathS[1]) != localSystem) {
+                        if (!json)
+                            logger->cout(fmt("%s " ANSI_WARNING "omitted" ANSI_NORMAL " (use '--all-systems' to show)", headerPrefix));
+                        else {
+                            logger->warn(fmt("%s omitted (use '--all-systems' to show)", concatStringsSep(".", attrPathS)));
+                        }
+                    } else {
+                        if (visitor.isDerivation())
+                            showDerivation();
+                        else
+                            throw Error("expected a derivation");
+                    }
                 }
 
                 else if (attrPath.size() > 0 && attrPathS[0] == "hydraJobs") {
@@ -1106,6 +1121,12 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                         else {
                             logger->warn(fmt("%s omitted (use '--legacy' to show)", concatStringsSep(".", attrPathS)));
                         }
+                    } else if (!showAllSystems && std::string(attrPathS[1]) != localSystem) {
+                        if (!json)
+                            logger->cout(fmt("%s " ANSI_WARNING "omitted" ANSI_NORMAL " (use '--all-systems' to show)", headerPrefix));
+                        else {
+                            logger->warn(fmt("%s omitted (use '--all-systems' to show)", concatStringsSep(".", attrPathS)));
+                        }
                     } else {
                         if (visitor.isDerivation())
                             showDerivation();
diff --git a/src/nix/show-config.cc b/src/nix/show-config.cc
index 29944e748..3530584f9 100644
--- a/src/nix/show-config.cc
+++ b/src/nix/show-config.cc
@@ -9,15 +9,44 @@ using namespace nix;
 
 struct CmdShowConfig : Command, MixJSON
 {
+    std::optional<std::string> name;
+
+    CmdShowConfig() {
+        expectArgs({
+            .label = {"name"},
+            .optional = true,
+            .handler = {&name},
+        });
+    }
+
     std::string description() override
     {
-        return "show the Nix configuration";
+        return "show the Nix configuration or the value of a specific setting";
     }
 
     Category category() override { return catUtility; }
 
     void run() override
     {
+        if (name) {
+            if (json) {
+                throw UsageError("'--json' is not supported when specifying a setting name");
+            }
+
+            std::map<std::string, Config::SettingInfo> settings;
+            globalConfig.getSettings(settings);
+            auto setting = settings.find(*name);
+
+            if (setting == settings.end()) {
+                throw Error("could not find setting '%1%'", *name);
+            } else {
+                const auto & value = setting->second.value;
+                logger->cout("%s", value);
+            }
+
+            return;
+        }
+
         if (json) {
             // FIXME: use appropriate JSON types (bool, ints, etc).
             logger->cout("%s", globalConfig.toJSON().dump());
diff --git a/tests/check-refs.nix b/tests/check-refs.nix
index 9d90b0920..99d69a226 100644
--- a/tests/check-refs.nix
+++ b/tests/check-refs.nix
@@ -67,4 +67,11 @@ rec {
     disallowedReferences = [test5];
   };
 
+  test11 = makeTest 11 {
+    __structuredAttrs = true;
+    unsafeDiscardReferences.out = true;
+    outputChecks.out.allowedReferences = [];
+    buildCommand = ''echo ${dep} > "''${outputs[out]}"'';
+  };
+
 }
diff --git a/tests/check-refs.sh b/tests/check-refs.sh
index 16bbabc40..65a72552a 100644
--- a/tests/check-refs.sh
+++ b/tests/check-refs.sh
@@ -40,3 +40,12 @@ nix-build -o $RESULT check-refs.nix -A test7
 
 # test10 should succeed (no disallowed references).
 nix-build -o $RESULT check-refs.nix -A test10
+
+if isDaemonNewer 2.12pre20230103; then
+    enableFeatures discard-references
+    restartDaemon
+
+    # test11 should succeed.
+    test11=$(nix-build -o $RESULT check-refs.nix -A test11)
+    [[ -z $(nix-store -q --references "$test11") ]]
+fi
diff --git a/tests/common.sh.in b/tests/common.sh.in
index 73c2d2309..74bbbc8ca 100644
--- a/tests/common.sh.in
+++ b/tests/common.sh.in
@@ -62,7 +62,7 @@ readLink() {
 }
 
 clearProfiles() {
-    profiles="$NIX_STATE_DIR"/profiles
+    profiles="$HOME"/.local/share/nix/profiles
     rm -rf $profiles
 }
 
diff --git a/tests/config.sh b/tests/config.sh
index 3d0da3cef..723f575ed 100644
--- a/tests/config.sh
+++ b/tests/config.sh
@@ -51,3 +51,8 @@ exp_features=$(nix show-config | grep '^experimental-features' | cut -d '=' -f 2
 [[ $prev != $exp_cores ]]
 [[ $exp_cores == "4242" ]]
 [[ $exp_features == "flakes nix-command" ]]
+
+# Test that it's possible to retrieve a single setting's value
+val=$(nix show-config | grep '^warn-dirty' | cut -d '=' -f  2 | xargs)
+val2=$(nix show-config warn-dirty)
+[[ $val == $val2 ]]
diff --git a/tests/export-graph.sh b/tests/export-graph.sh
index a1449b34e..4954a6cbc 100644
--- a/tests/export-graph.sh
+++ b/tests/export-graph.sh
@@ -4,7 +4,7 @@ clearStore
 clearProfiles
 
 checkRef() {
-    nix-store -q --references $TEST_ROOT/result | grep -q "$1" || fail "missing reference $1"
+    nix-store -q --references $TEST_ROOT/result | grep -q "$1"'$' || fail "missing reference $1"
 }
 
 # Test the export of the runtime dependency graph.
diff --git a/tests/flakes/common.sh b/tests/flakes/common.sh
index c333733c2..9d79080cd 100644
--- a/tests/flakes/common.sh
+++ b/tests/flakes/common.sh
@@ -20,9 +20,13 @@ writeSimpleFlake() {
       foo = import ./simple.nix;
       default = foo;
     };
+    packages.someOtherSystem = rec {
+      foo = import ./simple.nix;
+      default = foo;
+    };
 
     # To test "nix flake init".
-    legacyPackages.x86_64-linux.hello = import ./simple.nix;
+    legacyPackages.$system.hello = import ./simple.nix;
   };
 }
 EOF
diff --git a/tests/flakes/init.sh b/tests/flakes/init.sh
index 36cb9956a..2d4c77ba1 100644
--- a/tests/flakes/init.sh
+++ b/tests/flakes/init.sh
@@ -41,8 +41,8 @@ cat > $templatesDir/trivial/flake.nix <<EOF
   description = "A flake for building Hello World";
 
   outputs = { self, nixpkgs }: {
-    packages.x86_64-linux = rec {
-      hello = nixpkgs.legacyPackages.x86_64-linux.hello;
+    packages.$system = rec {
+      hello = nixpkgs.legacyPackages.$system.hello;
       default = hello;
     };
   };
diff --git a/tests/flakes/show.sh b/tests/flakes/show.sh
new file mode 100644
index 000000000..995de8dc3
--- /dev/null
+++ b/tests/flakes/show.sh
@@ -0,0 +1,39 @@
+source ./common.sh
+
+flakeDir=$TEST_ROOT/flake
+mkdir -p "$flakeDir"
+
+writeSimpleFlake "$flakeDir"
+cd "$flakeDir"
+
+
+# By default: Only show the packages content for the current system and no
+# legacyPackages at all
+nix flake show --json > show-output.json
+nix eval --impure --expr '
+let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
+in
+assert show_output.packages.someOtherSystem.default == {};
+assert show_output.packages.${builtins.currentSystem}.default.name == "simple";
+assert show_output.legacyPackages.${builtins.currentSystem} == {};
+true
+'
+
+# With `--all-systems`, show the packages for all systems
+nix flake show --json --all-systems > show-output.json
+nix eval --impure --expr '
+let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
+in
+assert show_output.packages.someOtherSystem.default.name == "simple";
+assert show_output.legacyPackages.${builtins.currentSystem} == {};
+true
+'
+
+# With `--legacy`, show the legacy packages
+nix flake show --json --legacy > show-output.json
+nix eval --impure --expr '
+let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
+in
+assert show_output.legacyPackages.${builtins.currentSystem}.hello.name == "simple";
+true
+'
diff --git a/tests/local.mk b/tests/local.mk
index 5ac1ede32..2aaaa67f9 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -17,6 +17,7 @@ nix_tests = \
   fetchMercurial.sh \
   gc-auto.sh \
   user-envs.sh \
+  user-envs-migration.sh \
   binary-cache.sh \
   multiple-outputs.sh \
   ca/build.sh \
@@ -113,6 +114,7 @@ nix_tests = \
   store-ping.sh \
   fetchClosure.sh \
   completions.sh \
+  flakes/show.sh \
   impure-derivations.sh \
   path-from-hash-part.sh \
   toString-path.sh
diff --git a/tests/nix_path.sh b/tests/nix_path.sh
index 2b222b4a1..d16fb4bb2 100644
--- a/tests/nix_path.sh
+++ b/tests/nix_path.sh
@@ -12,3 +12,8 @@ nix-instantiate --eval -E '<by-relative-path/simple.nix>' --restrict-eval
 
 [[ $(nix-instantiate --find-file by-absolute-path/simple.nix) = $PWD/simple.nix ]]
 [[ $(nix-instantiate --find-file by-relative-path/simple.nix) = $PWD/simple.nix ]]
+
+unset NIX_PATH
+
+[[ $(nix-instantiate --option nix-path by-relative-path=. --find-file by-relative-path/simple.nix) = "$PWD/simple.nix" ]]
+[[ $(NIX_PATH= nix-instantiate --option nix-path by-relative-path=. --find-file by-relative-path/simple.nix) = "$PWD/simple.nix" ]]
diff --git a/tests/containers.nix b/tests/nixos/containers/containers.nix
index a4856b2df..c8ee78a4a 100644
--- a/tests/containers.nix
+++ b/tests/nixos/containers/containers.nix
@@ -1,12 +1,7 @@
 # Test whether we can run a NixOS container inside a Nix build using systemd-nspawn.
-{ nixpkgs, system, overlay }:
+{ lib, nixpkgs, ... }:
 
-with import (nixpkgs + "/nixos/lib/testing-python.nix") {
-  inherit system;
-  extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
-};
-
-makeTest ({
+{
   name = "containers";
 
   nodes =
@@ -65,4 +60,4 @@ makeTest ({
     host.succeed("[[ $(cat ./result/msg) = 'Hello World' ]]")
   '';
 
-})
+}
diff --git a/tests/id-test.nix b/tests/nixos/containers/id-test.nix
index 8eb9d38f9..8eb9d38f9 100644
--- a/tests/id-test.nix
+++ b/tests/nixos/containers/id-test.nix
diff --git a/tests/systemd-nspawn.nix b/tests/nixos/containers/systemd-nspawn.nix
index 424436b3f..424436b3f 100644
--- a/tests/systemd-nspawn.nix
+++ b/tests/nixos/containers/systemd-nspawn.nix
diff --git a/tests/github-flakes.nix b/tests/nixos/github-flakes.nix
index a8b036b17..e4d347691 100644
--- a/tests/github-flakes.nix
+++ b/tests/nixos/github-flakes.nix
@@ -1,14 +1,9 @@
-{ nixpkgs, system, overlay }:
-
-with import (nixpkgs + "/nixos/lib/testing-python.nix") {
-  inherit system;
-  extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
-};
-
+{ lib, config, nixpkgs, ... }:
 let
+  pkgs = config.nodes.client.nixpkgs.pkgs;
 
   # Generate a fake root CA and a fake api.github.com / github.com / channels.nixos.org certificate.
-  cert = pkgs.runCommand "cert" { buildInputs = [ pkgs.openssl ]; }
+  cert = pkgs.runCommand "cert" { nativeBuildInputs = [ pkgs.openssl ]; }
     ''
       mkdir -p $out
 
@@ -92,8 +87,6 @@ let
     '';
 in
 
-makeTest (
-
 {
   name = "github-flakes";
 
@@ -207,4 +200,4 @@ makeTest (
     client.succeed("nix build nixpkgs#fuse --tarball-ttl 0")
   '';
 
-})
+}
diff --git a/tests/nix-copy-closure.nix b/tests/nixos/nix-copy-closure.nix
index 2dc164ae4..66cbfb033 100644
--- a/tests/nix-copy-closure.nix
+++ b/tests/nixos/nix-copy-closure.nix
@@ -1,13 +1,16 @@
 # Test ‘nix-copy-closure’.
 
-{ nixpkgs, system, overlay }:
+{ lib, config, nixpkgs, hostPkgs, ... }:
 
-with import (nixpkgs + "/nixos/lib/testing-python.nix") {
-  inherit system;
-  extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
-};
+let
+  pkgs = config.nodes.client.nixpkgs.pkgs;
 
-makeTest (let pkgA = pkgs.cowsay; pkgB = pkgs.wget; pkgC = pkgs.hello; pkgD = pkgs.tmux; in {
+  pkgA = pkgs.cowsay;
+  pkgB = pkgs.wget;
+  pkgC = pkgs.hello;
+  pkgD = pkgs.tmux;
+
+in {
   name = "nix-copy-closure";
 
   nodes =
@@ -74,4 +77,4 @@ makeTest (let pkgA = pkgs.cowsay; pkgB = pkgs.wget; pkgC = pkgs.hello; pkgD = pk
     # )
     # client.succeed("nix-store --check-validity ${pkgC}")
   '';
-})
+}
diff --git a/tests/nss-preload.nix b/tests/nixos/nss-preload.nix
index 5a6ff3f68..cef62e95b 100644
--- a/tests/nss-preload.nix
+++ b/tests/nixos/nss-preload.nix
@@ -1,11 +1,9 @@
-{ nixpkgs, system, overlay }:
-
-with import (nixpkgs + "/nixos/lib/testing-python.nix") {
-  inherit system;
-  extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
-};
+{ lib, config, nixpkgs, ... }:
 
 let
+
+  pkgs = config.nodes.client.nixpkgs.pkgs;
+
   nix-fetch = pkgs.writeText "fetch.nix" ''
     derivation {
         # This derivation is an copy from what is available over at
@@ -41,9 +39,7 @@ let
   '';
 in
 
-makeTest (
-
-rec {
+{
   name = "nss-preload";
 
   nodes = {
@@ -122,4 +118,4 @@ rec {
           nix-build ${nix-fetch} >&2
           """)
   '';
-})
+}
diff --git a/tests/remote-builds.nix b/tests/nixos/remote-builds.nix
index 9f88217fe..696cd2652 100644
--- a/tests/remote-builds.nix
+++ b/tests/nixos/remote-builds.nix
@@ -1,15 +1,9 @@
 # Test Nix's remote build feature.
 
-{ nixpkgs, system, overlay }:
-
-with import (nixpkgs + "/nixos/lib/testing-python.nix") {
-  inherit system;
-  extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
-};
-
-makeTest (
+{ config, lib, hostPkgs, ... }:
 
 let
+  pkgs = config.nodes.client.nixpkgs.pkgs;
 
   # The configuration of the remote builders.
   builder =
@@ -75,7 +69,7 @@ in
 
     # Create an SSH key on the client.
     subprocess.run([
-      "${pkgs.openssh}/bin/ssh-keygen", "-t", "ed25519", "-f", "key", "-N", ""
+      "${hostPkgs.openssh}/bin/ssh-keygen", "-t", "ed25519", "-f", "key", "-N", ""
     ], capture_output=True, check=True)
     client.succeed("mkdir -p -m 700 /root/.ssh")
     client.copy_from_host("key", "/root/.ssh/id_ed25519")
@@ -109,4 +103,4 @@ in
     builder1.block()
     client.succeed("nix-build ${expr nodes.client.config 4}")
   '';
-})
+}
diff --git a/tests/setuid.nix b/tests/nixos/setuid.nix
index 6784615e4..2b66320dd 100644
--- a/tests/setuid.nix
+++ b/tests/nixos/setuid.nix
@@ -1,13 +1,12 @@
 # Verify that Linux builds cannot create setuid or setgid binaries.
 
-{ nixpkgs, system, overlay }:
+{ lib, config, nixpkgs, ... }:
 
-with import (nixpkgs + "/nixos/lib/testing-python.nix") {
-  inherit system;
-  extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
-};
+let
+  pkgs = config.nodes.machine.nixpkgs.pkgs;
 
-makeTest {
+in
+{
   name = "setuid";
 
   nodes.machine =
diff --git a/tests/sourcehut-flakes.nix b/tests/nixos/sourcehut-flakes.nix
index b77496ab6..a76fed020 100644
--- a/tests/sourcehut-flakes.nix
+++ b/tests/nixos/sourcehut-flakes.nix
@@ -1,12 +1,8 @@
-{ nixpkgs, system, overlay }:
-
-with import (nixpkgs + "/nixos/lib/testing-python.nix")
-{
-  inherit system;
-  extraConfigurations = [{ nixpkgs.overlays = [ overlay ]; }];
-};
+{ lib, config, hostPkgs, nixpkgs, ... }:
 
 let
+  pkgs = config.nodes.sourcehut.nixpkgs.pkgs;
+
   # Generate a fake root CA and a fake git.sr.ht certificate.
   cert = pkgs.runCommand "cert" { buildInputs = [ pkgs.openssl ]; }
     ''
@@ -64,8 +60,6 @@ let
 
 in
 
-makeTest (
-
   {
     name = "sourcehut-flakes";
 
@@ -164,4 +158,4 @@ makeTest (
       client.succeed("nix build nixpkgs#fuse --tarball-ttl 0")
     '';
 
-  })
+}
diff --git a/tests/remote-store.sh b/tests/remote-store.sh
index 31210ab47..1ae126794 100644
--- a/tests/remote-store.sh
+++ b/tests/remote-store.sh
@@ -30,7 +30,3 @@ NIX_REMOTE= nix-store --dump-db > $TEST_ROOT/d2
 cmp $TEST_ROOT/d1 $TEST_ROOT/d2
 
 killDaemon
-
-user=$(whoami)
-[ -e $NIX_STATE_DIR/gcroots/per-user/$user ]
-[ -e $NIX_STATE_DIR/profiles/per-user/$user ]
diff --git a/tests/restricted.sh b/tests/restricted.sh
index 9bd16cf51..3b6ee2af1 100644
--- a/tests/restricted.sh
+++ b/tests/restricted.sh
@@ -17,6 +17,9 @@ nix-instantiate --restrict-eval --eval -E 'builtins.readDir ../src/nix-channel'
 (! nix-instantiate --restrict-eval --eval -E 'let __nixPath = [ { prefix = "foo"; path = ./.; } ]; in <foo>')
 nix-instantiate --restrict-eval --eval -E 'let __nixPath = [ { prefix = "foo"; path = ./.; } ]; in <foo>' -I src=.
 
+# no default NIX_PATH
+(unset NIX_PATH; ! nix-instantiate --restrict-eval --find-file .)
+
 p=$(nix eval --raw --expr "builtins.fetchurl file://$(pwd)/restricted.sh" --impure --restrict-eval --allowed-uris "file://$(pwd)")
 cmp $p restricted.sh
 
diff --git a/tests/user-envs-migration.sh b/tests/user-envs-migration.sh
new file mode 100644
index 000000000..467c28fbb
--- /dev/null
+++ b/tests/user-envs-migration.sh
@@ -0,0 +1,35 @@
+# Test that the migration of user environments
+# (https://github.com/NixOS/nix/pull/5226) does preserve everything
+
+source common.sh
+
+if isDaemonNewer "2.4pre20211005"; then
+    exit 99
+fi
+
+
+killDaemon
+unset NIX_REMOTE
+
+clearStore
+clearProfiles
+rm -rf ~/.nix-profile
+
+# Fill the environment using the older Nix
+PATH_WITH_NEW_NIX="$PATH"
+export PATH="$NIX_DAEMON_PACKAGE/bin:$PATH"
+
+nix-env -f user-envs.nix -i foo-1.0
+nix-env -f user-envs.nix -i bar-0.1
+
+# Migrate to the new profile dir, and ensure that everything’s there
+export PATH="$PATH_WITH_NEW_NIX"
+nix-env -q # Trigger the migration
+( [[ -L ~/.nix-profile ]] && \
+    [[ $(readlink ~/.nix-profile) == ~/.local/share/nix/profiles/profile ]] ) || \
+    fail "The nix profile should point to the new location"
+
+(nix-env -q | grep foo && nix-env -q | grep bar && \
+    [[ -e ~/.nix-profile/bin/foo ]] && \
+    [[ $(nix-env --list-generations | wc -l) == 2 ]]) ||
+    fail "The nix profile should have the same content as before the migration"