nix-super/doc/manual/source/advanced-topics/distributed-builds.md
John Ericson eb7d7780b1 Rename doc/manual{src -> source}
This is needed to avoid this
https://github.com/mesonbuild/meson/issues/13774 when we go back to
making our subproject directory `src`.
2024-10-14 11:21:24 -04:00

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# Remote Builds
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
`x86_64-darwin` on an `i686-linux` machine, Nix can automatically
forward the build to a `x86_64-darwin` machine, if available.
To forward a build to a remote machine, its 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.
```console
$ nix store info --store ssh://mac
```
will try to connect to the machine named `mac`. It is possible to
specify an SSH identity file as part of the remote store URI, e.g.
```console
$ nix store info --store ssh://mac?ssh-key=/home/alice/my-key
```
Since builds should be non-interactive, the key should not have a
passphrase. Alternatively, you can load identities ahead of time into
`ssh-agent` or `gpg-agent`.
If you get the error
```console
bash: nix-store: command not found
error: cannot connect to 'mac'
```
then you need to ensure that the `PATH` of non-interactive login shells
contains Nix.
The [list of remote build machines](@docroot@/command-ref/conf-file.md#conf-builders) can be specified on the command line or in the Nix configuration file.
For example, the following command allows you to build a derivation for `x86_64-darwin` on a Linux machine:
```console
$ uname
Linux
$ nix build --impure \
--expr '(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
```
It is possible to specify multiple build machines separated by a semicolon or a newline, e.g.
```console
--builders 'ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd'
```
Remote build machines can also be configured in [`nix.conf`](@docroot@/command-ref/conf-file.md), e.g.
builders = ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd
Finally, remote build machines can be configured in a separate configuration
file included in `builders` via the syntax `@/path/to/file`. For example,
builders = @/etc/nix/machines
causes the list of machines in `/etc/nix/machines` to be included.
(This is the default.)