aboutsummaryrefslogtreecommitdiff
path: root/doc/manual/advanced-topics
diff options
context:
space:
mode:
Diffstat (limited to 'doc/manual/advanced-topics')
-rw-r--r--doc/manual/advanced-topics/distributed-builds.xml211
1 files changed, 144 insertions, 67 deletions
diff --git a/doc/manual/advanced-topics/distributed-builds.xml b/doc/manual/advanced-topics/distributed-builds.xml
index 1957e1105..20fd6a0cf 100644
--- a/doc/manual/advanced-topics/distributed-builds.xml
+++ b/doc/manual/advanced-topics/distributed-builds.xml
@@ -4,71 +4,109 @@
version="5.0"
xml:id='chap-distributed-builds'>
-<title>Distributed Builds</title>
-
-<para>Nix supports distributed builds, where a local Nix installation can
-forward Nix builds to other machines over the network. This allows
-multiple builds to be performed in parallel (thus improving
-performance) and allows Nix to perform multi-platform builds in a
-semi-transparent way. For instance, if you perform a build for a
-<literal>x86_64-darwin</literal> on an <literal>i686-linux</literal>
-machine, Nix can automatically forward the build to a
-<literal>x86_64-darwin</literal> machine, if available.</para>
-
-<para>You can enable distributed builds by setting the environment
-variable <envar>NIX_BUILD_HOOK</envar> to point to a program that Nix
-will call whenever it wants to build a derivation. The build hook
-(typically a shell or Perl script) can decline the build, in which Nix
-will perform it in the usual way if possible, or it can accept it, in
-which case it is responsible for somehow getting the inputs of the
-build to another machine, doing the build there, and getting the
-results back.</para>
-
-<example xml:id='ex-remote-systems'><title>Remote machine configuration:
-<filename>remote-systems.conf</filename></title>
-<programlisting>
-nix@mcflurry.labs.cs.uu.nl x86_64-darwin /home/nix/.ssh/id_quarterpounder_auto 2
-nix@scratchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 1 kvm
-nix@itchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 2
-nix@poochie.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 2 kvm perf
-</programlisting>
-</example>
-
-<para>Nix ships with a build hook that should be suitable for most
-purposes. It uses <command>ssh</command> and
-<command>nix-copy-closure</command> to copy the build inputs and
-outputs and perform the remote build. To use it, you should set
-<envar>NIX_BUILD_HOOK</envar> to
-<filename><replaceable>prefix</replaceable>/libexec/nix/build-remote</filename>.
-You should also define a list of available build machines and point
-the environment variable <envar>NIX_REMOTE_SYSTEMS</envar> to
-it. <envar>NIX_REMOTE_SYSTEMS</envar> must be an absolute path. An
-example configuration is shown in <xref linkend='ex-remote-systems'
-/>. Each line in the file specifies a machine, with the following
-bits of information:
+<title>Remote Builds</title>
+
+<para>Nix supports remote builds, where a local Nix installation can
+forward Nix builds to other machines. This allows multiple builds to
+be performed in parallel and allows Nix to perform multi-platform
+builds in a semi-transparent way. For instance, if you perform a
+build for a <literal>x86_64-darwin</literal> on an
+<literal>i686-linux</literal> machine, Nix can automatically forward
+the build to a <literal>x86_64-darwin</literal> machine, if
+available.</para>
+
+<para>To forward a build to a remote machine, it’s required that the
+remote machine is accessible via SSH and that it has Nix
+installed. You can test whether connecting to the remote Nix instance
+works, e.g.
+
+<screen>
+$ nix ping-store --store ssh://mac
+</screen>
+
+will try to connect to the machine named <literal>mac</literal>. It is
+possible to specify an SSH identity file as part of the remote store
+URI, e.g.
+
+<screen>
+$ nix ping-store --store ssh://mac?ssh-key=/home/alice/my-key
+</screen>
+
+Since builds should be non-interactive, the key should not have a
+passphrase. Alternatively, you can load identities ahead of time into
+<command>ssh-agent</command> or <command>gpg-agent</command>.</para>
+
+<para>If you get the error
+
+<screen>
+bash: nix-store: command not found
+error: cannot connect to 'mac'
+</screen>
+
+then you need to ensure that the <envar>PATH</envar> of
+non-interactive login shells contains Nix.</para>
+
+<warning><para>If you are building via the Nix daemon, it is the Nix
+daemon user account (that is, <literal>root</literal>) that should
+have SSH access to the remote machine. If you can’t or don’t want to
+configure <literal>root</literal> to be able to access to remote
+machine, you can use a private Nix store instead by passing
+e.g. <literal>--store ~/my-nix</literal>.</para></warning>
+
+<para>The list of remote machines can be specified on the command line
+or in the Nix configuration file. The former is convenient for
+testing. For example, the following command allows you to build a
+derivation for <literal>x86_64-darwin</literal> on a Linux machine:
+
+<screen>
+$ uname
+Linux
+
+$ nix build \
+ '(with import &lt;nixpkgs> { system = "x86_64-darwin"; }; runCommand "foo" {} "uname > $out")' \
+ --builders 'ssh://mac x86_64-darwin'
+[1/0/1 built, 0.0 MiB DL] building foo on ssh://mac
+
+$ cat ./result
+Darwin
+</screen>
+
+It is possible to specify multiple builders separated by a semicolon
+or a newline, e.g.
+
+<screen>
+ --builders 'ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd'
+</screen>
+</para>
+
+<para>Each machine specification consists of the following elements,
+separated by spaces. Only the first element is required.
<orderedlist>
- <listitem><para>The name of the remote machine, with optionally the
- user under which the remote build should be performed. This is
- actually passed as an argument to <command>ssh</command>, so it can
- be an alias defined in your
+ <listitem><para>The URI of the remote store in the format
+ <literal>ssh://[<replaceable>username</replaceable>@]<replaceable>hostname</replaceable></literal>,
+ e.g. <literal>ssh://nix@mac</literal> or
+ <literal>ssh://mac</literal>. For backward compatibility,
+ <literal>ssh://</literal> may be omitted. The hostname may be an
+ alias defined in your
<filename>~/.ssh/config</filename>.</para></listitem>
<listitem><para>A comma-separated list of Nix platform type
identifiers, such as <literal>x86_64-darwin</literal>. It is
possible for a machine to support multiple platform types, e.g.,
- <literal>i686-linux,x86_64-linux</literal>.</para></listitem>
+ <literal>i686-linux,x86_64-linux</literal>. If omitted, this
+ defaults to the local platform type.</para></listitem>
- <listitem><para>The SSH private key to be used to log in to the
- remote machine. Since builds should be non-interactive, this key
- should not have a passphrase!</para></listitem>
+ <listitem><para>The SSH identity file to be used to log in to the
+ remote machine. If omitted, SSH will use its regular
+ identities.</para></listitem>
- <listitem><para>The maximum number of builds that
- <filename>build-remote</filename> will execute in parallel on the
- machine. Typically this should be equal to the number of CPU cores.
- For instance, the machine <literal>itchy</literal> in the example
- will execute up to 8 builds in parallel.</para></listitem>
+ <listitem><para>The maximum number of builds that Nix will execute
+ in parallel on the machine. Typically this should be equal to the
+ number of CPU cores. For instance, the machine
+ <literal>itchy</literal> in the example will execute up to 8 builds
+ in parallel.</para></listitem>
<listitem><para>The “speed factor”, indicating the relative speed of
the machine. If there are multiple machines of the right type, Nix
@@ -76,30 +114,69 @@ bits of information:
<listitem><para>A comma-separated list of <emphasis>supported
features</emphasis>. If a derivation has the
- <varname>requiredSystemFeatures</varname> attribute, then
- <filename>build-remote</filename> will only perform the
- derivation on a machine that has the specified features. For
- instance, the attribute
+ <varname>requiredSystemFeatures</varname> attribute, then Nix will
+ only perform the derivation on a machine that has the specified
+ features. For instance, the attribute
<programlisting>
requiredSystemFeatures = [ "kvm" ];
</programlisting>
will cause the build to be performed on a machine that has the
- <literal>kvm</literal> feature (i.e., <literal>scratchy</literal> in
- the example above).</para></listitem>
+ <literal>kvm</literal> feature.</para></listitem>
<listitem><para>A comma-separated list of <emphasis>mandatory
features</emphasis>. A machine will only be used to build a
derivation if all of the machine’s mandatory features appear in the
- derivation’s <varname>requiredSystemFeatures</varname> attribute.
- Thus, in the example, the machine <literal>poochie</literal> will
- only do derivations that have
- <varname>requiredSystemFeatures</varname> set to <literal>["kvm"
- "perf"]</literal> or <literal>["perf"]</literal>.</para></listitem>
+ derivation’s <varname>requiredSystemFeatures</varname>
+ attribute..</para></listitem>
</orderedlist>
-</para>
+For example, the machine specification
+
+<programlisting>
+nix@scratchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 1 kvm
+nix@itchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 2
+nix@poochie.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 1 2 kvm benchmark
+</programlisting>
+
+specifies several machines that can perform
+<literal>i686-linux</literal> builds. However,
+<literal>poochie</literal> will only do builds that have the attribute
+
+<programlisting>
+requiredSystemFeatures = [ "benchmark" ];
+</programlisting>
+
+or
+
+<programlisting>
+requiredSystemFeatures = [ "benchmark" "kvm" ];
+</programlisting>
+
+<literal>itchy</literal> cannot do builds that require
+<literal>kvm</literal>, but <literal>scratchy</literal> does support
+such builds. For regular builds, <literal>itchy</literal> will be
+preferred over <literal>scratchy</literal> because it has a higher
+speed factor.</para>
+
+<para>Remote builders can also be configured in
+<filename>nix.conf</filename>, e.g.
+
+<programlisting>
+builders = ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd
+</programlisting>
+
+Finally, remote builders can be configured in a separate configuration
+file included in <option>builders</option> via the syntax
+<literal>@<replaceable>file</replaceable></literal>. For example,
+
+<programlisting>
+builders = @/etc/nix/machines
+</programlisting>
+
+causes the list of machines in <filename>/etc/nix/machines</filename>
+to be included. (This is the default.)</para>
</chapter>