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diff --git a/third_party/nix/doc/manual/advanced-topics/distributed-builds.xml b/third_party/nix/doc/manual/advanced-topics/distributed-builds.xml new file mode 100644 index 0000000000..9ac4a92cd5 --- /dev/null +++ b/third_party/nix/doc/manual/advanced-topics/distributed-builds.xml @@ -0,0 +1,190 @@ +<chapter xmlns="http://docbook.org/ns/docbook" + xmlns:xlink="http://www.w3.org/1999/xlink" + xmlns:xi="http://www.w3.org/2001/XInclude" + version="5.0" + xml:id='chap-distributed-builds'> + +<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 <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. +To leave a field at its default, set it to <literal>-</literal>. + +<orderedlist> + + <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>. If omitted, this + defaults to the local platform type.</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 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 + will prefer the fastest, taking load into account.</para></listitem> + + <listitem><para>A comma-separated list of <emphasis>supported + features</emphasis>. If a derivation has the + <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.</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..</para></listitem> + +</orderedlist> + +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> + +<para>If you want the builders to use caches, you likely want to set +the option <link linkend='conf-builders-use-substitutes'><literal>builders-use-substitutes</literal></link> +in your local <filename>nix.conf</filename>.</para> + +<para>To build only on remote builders and disable building on the local machine, +you can use the option <option>--max-jobs 0</option>.</para> + +</chapter> |