Distributed build: Difference between revisions
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m →Modify the local machine's Nix config to know about the remote machine.: Remove erroneous bold header |
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When your '''local machine''' is too slow or doesn't have the right CPU architecture or operating system for the Nix derivation you want to build, you can delegate the build to some other '''remote machine'''. For this you need | When your '''local machine''' is too slow or doesn't have the right CPU architecture or operating system for the Nix derivation you want to build, you can delegate the build to some other '''remote machine'''. For this you need | ||
# the '''Nix package manager installed on both machines'''; just follow the [https://nixos.org/download/ official installation instructions] | # the '''Nix package manager installed on both machines'''; just follow the [https://nixos.org/download/ official installation instructions] and prefer the normal "multi-user" install. You don't need to run NixOS; any operating system like Debian, Ubuntu, Arch, MacOS or others where the Nix package manager can be installed, should work. | ||
# '''SSH access from the local to the remote machine'''. | # '''SSH access from the local to the remote machine'''. | ||
# '''modify the local machine's Nix config to know about the remote machine'''. | # '''modify the local machine's Nix config to know about the remote machine'''. | ||
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! SSH Connection Requirements | ! SSH Connection Requirements | ||
|- | |- | ||
| '''Multi-user''' || '''Multi-user''' || '''Local''' | | '''Multi-user''' || '''Multi-user''' || '''Local:''' {{ic|root}} user ------------SSH----> '''Remote''': ''any'' user '''(most frequent case)''' | ||
|- | |- | ||
| Single-user || Multi-user || '' | | Single-user || Multi-user || '''Local:''' ''Your'' single-user -----SSH----> '''Remote''': ''any'' user | ||
|- | |- | ||
| Multi-user || Single-user || '''Local''' | | Multi-user || Single-user || '''Local:''' {{ic|root}} user ------------SSH----> '''Remote''': ''your'' single-user for which Nix is installed with their UID (see [https://nixos.org/manual/nix/stable/installation/single-user.html Nix manual page]). | ||
|- | |- | ||
| Single-user || | | Single-user || Single-user || '''Local:''' ''Your'' single-user -----SSH----> '''Remote''': ''your single-user'' each of which Nix is installed for with their UID (see [https://nixos.org/manual/nix/stable/installation/single-user.html Nix manual page]). | ||
|} | |} | ||
The thing to know about the '''"Multi-user"''' installation is that '''Nix is installed with a "nix-daemon" background process that runs as root''' and actually manages the builds on your behalf. So when you call '''"nix build ..." as a non-root user, this is delegated to the nix-daemon''' process, which runs as root. And this process can further delegate the build to a remote builder; that's why the '''local machine's root user''' needs the SSH access. | The thing to know about the '''"Multi-user"''' installation is that '''Nix is installed with a "nix-daemon" background process that runs as root''' and actually manages the builds on your behalf. So when you call '''"nix build ..." as a non-root user, this is delegated to the nix-daemon''' process, which runs as root. And this process can further delegate the build to a remote builder; that's why the '''local machine's root user''' needs the SSH access. | ||
{{Tip|The best | {{Tip|The best test to check that the SSH access works for Nix is to run on your local machine: | ||
nix store ping --store ssh://<REMOTE-BUILDER> | <code>nix store ping --store ssh://<REMOTE-BUILDER></code> | ||
Where <REMOTE-BUILDER> is the remote builder's IP address, host address or whatever name you configure in ~/.ssh/config or /root/.ssh/config, including the user@ prefix.}} | Where <code><REMOTE-BUILDER></code> is the remote builder's IP address, host address or whatever name you configure in ~/.ssh/config or /root/.ssh/config, including the user@ prefix.}} | ||
An alternative check is: | An alternative check is: | ||
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For the common case where your local Nix is installed system-wide in multi-user mode, create a user on the '''remote''' machine that will have an unwriteable home directory, with a {{ic|~/.ssh/authorized_keys}} in it, that will allow SSH access to that user without a passphrase. The steps are: | For the common case where your local Nix is installed system-wide in multi-user mode, create a user on the '''remote''' machine that will have an unwriteable home directory, with a {{ic|~/.ssh/authorized_keys}} in it, that will allow SSH access to that user without a passphrase. The steps are: | ||
* {{ic|ssh}} to the remote builder. | |||
* Run (requires privileges) {{ic|useradd -m nixremote}}; {{ic|-m}} makes sure a home directory is created for the {{ic|nixremote}} user. | |||
* Run (requires privileges) {{ic|usermod nixremote -L}}; {{ic|-L}} locks the user such that nobody will be able to {{ic|su}} to it | |||
* Run (requires privileges) {{ic|mkdir ~nixremote/.ssh}}. Make sure to run this command as {{ic|nixremote}} user or {{ic|chown}} it afterwards | |||
If your '''remote builder''' has Nix installed system-wide in multi-user mode, but you're not running NixOS, '''you may need to add something like the following to your''' {{ic|/etc/ssh/sshd_config}} on this remote machine: | If your '''remote builder''' has Nix installed system-wide in multi-user mode, but you're not running NixOS, '''you may need to add something like the following to your''' {{ic|/etc/ssh/sshd_config}} on this remote machine: | ||
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You may also want to make nix on '''the remote machine''' trust that new user by adding it to {{ic|nix.settings.trusted-users}} if it's using NixOS, or by manually adding <code><nowiki>trusted-users = nixremote</nowiki></code> to {{ic|/etc/nix/nix.conf}}. | You may also want to make nix on '''the remote machine''' trust that new user by adding it to {{ic|nix.settings.trusted-users}} if it's using NixOS, or by manually adding <code><nowiki>trusted-users = nixremote</nowiki></code> to {{ic|/etc/nix/nix.conf}}. | ||
== | == Modify the local machine's Nix config to know about the remote machine. == | ||
The Nix package manager '''on your local machine''' '''needs to know that the remote builder exists''' and what its ''supported features'' are. See [https://nixos.org/manual/nix/stable/command-ref/conf-file#conf-system-features official supportedFeatures documentation]. | The Nix package manager '''on your local machine''' '''needs to know that the remote builder exists''' and what its ''supported features'' are. See [https://nixos.org/manual/nix/stable/command-ref/conf-file#conf-system-features official supportedFeatures documentation]. | ||
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# systems = ["x86_64-linux" "aarch64-linux" "riscv64-linux"]; | # systems = ["x86_64-linux" "aarch64-linux" "riscv64-linux"]; | ||
system = "x86_64-linux"; | system = "x86_64-linux"; | ||
# Nix custom ssh-variant that avoids lots of "trusted-users" settings pain | |||
protocol = "ssh-ng"; | protocol = "ssh-ng"; | ||
# default is 1 but may keep the builder idle in between builds | # default is 1 but may keep the builder idle in between builds | ||
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nix.distributedBuilds = true; | nix.distributedBuilds = true; | ||
# optional, useful when the builder has a faster internet connection than yours | # optional, useful when the builder has a faster internet connection than yours | ||
nix. | nix.settings = { | ||
builders-use-substitutes = true | builders-use-substitutes = true; | ||
}; | |||
} | } | ||
</nowiki>}} | </nowiki>}} | ||
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== See also == | == See also == | ||
* [https://github.com/NixOS/nix/blob/ | * [https://github.com/NixOS/nix/blob/a6e6da3b0c579fc540acb00748fe3fd1858b9d99/tests/nixos/remote-builds.nix#L11-L21 The NixOS Remote Builds Test Case] | ||
* [https://nixos.org/nix-dev/2015-September/018255.html Mail to nixos-dev about setting up remote builds by Russell O'Connor] | * [https://nixos.org/nix-dev/2015-September/018255.html Mail to nixos-dev about setting up remote builds by Russell O'Connor] | ||
* [https://gist.github.com/danbst/09c3f6cd235ae11ccd03215d4542f7e7 A step-by-step guide on remote Firefox building through bastion host] | * [https://gist.github.com/danbst/09c3f6cd235ae11ccd03215d4542f7e7 A step-by-step guide on remote Firefox building through bastion host] | ||