Official NixOS Wiki

Binary Cache: Difference between revisions

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imported>Knedlsepp
Fixed the chown line so that the nix-serve user has access to it.
I think this https://discourse.nixos.org/t/garnix-blog-stop-trusting-nix-caches/70177 raises a valid point that should be added to the wiki to educate people about the implications.
 
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{{Expansion|What is the format of a binary cache? How does it differ from a local/remote Nix store? See [https://github.com/NixOS/nix/pull/6870 `NixOS/nix` PR #6870]. (Maybe even splitting it into a guide and a reference?)}}
A binary cache builds Nix packages and caches the result for other machines. Any machine with Nix installed can be a binary cache for another one, no matter the operating system.
A binary cache builds Nix packages and caches the result for other machines. Any machine with Nix installed can be a binary cache for another one, no matter the operating system.


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=== 1. Generating a private/public keypair ===
=== 1. Generating a private/public keypair ===


A keypair is necessary to sign Nix packages.  
A keypair is necessary to sign Nix packages. Replace <code>binarycache.example.com</code> with your domain.


{{bc|
{{bc|
$ nix-store --generate-binary-cache-key binarycache.example.com cache-priv-key.pem cache-pub-key.pem
cd /var
# mv cache-priv-key.pem /var/cache-priv-key.pem
nix-store --generate-binary-cache-key binarycache.example.com cache-priv-key.pem cache-pub-key.pem
# chown nix-serve /var/cache-priv-key.pem
chown nix-serve cache-priv-key.pem
# chmod 600 /var/cache-priv-key.pem
chmod 600 cache-priv-key.pem
cat cache-pub-key.pem
}}
}}


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services.nginx = {
services.nginx = {
   enable = true;
   enable = true;
  recommendedProxySettings = true;
   virtualHosts = {
   virtualHosts = {
     # ... existing hosts config etc. ...
     # ... existing hosts config etc. ...
     "binarycache.example.com" = {
     "binarycache.example.com" = {
      serverAliases = [ "binarycache" ];
       locations."/".proxyPass = "http://${config.services.nix-serve.bindAddress}:${toString config.services.nix-serve.port}";
       locations."/".extraConfig = ''
        proxy_pass http://localhost:${toString config.services.nix-serve.port};
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      '';
     };
     };
   };
   };
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== Using a binary cache ==
== Using a binary cache ==


To configure Nix to use a certain binary cache, refer to the Nix manual.<ref group="cf.">[https://nixos.org/nix/manual/#ch-files Nix Manual, 21. Files]</ref> Add the binary cache as substituter (see the options {{ic|substituters}} and {{ic|extra-substituters}}) and the public key to the trusted keys (see {{ic|trusted-public-keys}}).
To configure Nix to use a certain binary cache, refer to the Nix manual.<ref group="cf.">[https://nixos.org/nix/manual/#ch-files Nix Manual, 21. Files]</ref> Add the binary cache as substituter (see the option {{ic|substituters}}) and the public key to the trusted keys (see {{ic|trusted-public-keys}}).
{{Warning|When adding a third-party binary cache you now trust all packages being served from that cache. Make sure this is a conscious decision. Trusting arbitrary caches can open you up to suppply chain attacks.
For more context: https://discourse.nixos.org/t/garnix-blog-stop-trusting-nix-caches/70177 (if source unavailable, https://web.archive.org/web/20251001172145/https://garnix.io/blog/stop-trusting-nix-caches)}}{{tip|If you are facing problems with derivations not being in a cache, try switching to a release version. Most caches will have many derivations for a specific release.}}
 
Permanent use of binary cache:
 
<syntaxhighlight lang="nix">
# /etc/nixos/configuration.nix
 
  nix = {
    settings = {
      substituters = [
        "http://binarycache.example.com"
        "https://nix-community.cachix.org"
        "https://cache.nixos.org/"
      ];
      trusted-public-keys = [
        "binarycache.example.com-1:dsafdafDFW123fdasfa123124FADSAD"
        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
      ];
    };
  };
</syntaxhighlight>As described on [https://search.nixos.org/options?show=nix.settings.substituters&type=packages&query=substituters search.nixos.org] by default <nowiki>https://cache.nixos.org/</nowiki> is added to the substituters. You may need to use lib.mkForce to override this and ensure your substituter is the primary choice.<syntaxhighlight>
# /etc/nixos/configuration.nix
 
 
{ config, lib, pkgs, ... }:
 
{
  nix = {
    settings = {
      substituters = lib.mkForce [
        "http://binarycache.example.com"
      ];
      trusted-public-keys = [
        "binarycache.example.com-1:dsafdafDFW123fdasfa123124FADSAD"
      ];
    };
  };
}
</syntaxhighlight>{{Warning|Keys that are entered incorrectly or are otherwise invalid, aside from preventing you from benefiting from the cached derivations, may also prevent you from rebuilding your system. This is most likely to occur after garbage collection (e.g., via <code>nix-collect-garbage -d</code>). Consult [https://github.com/NixOS/nix/issues/8271 NixOS/nix#8271] for additional details and a workaround.}}
 
Temporary use of binary cache:


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
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warning: you did not specify '--add-root'; the result might be removed by the garbage collector
warning: you did not specify '--add-root'; the result might be removed by the garbage collector
/nix/store/gdh8165b7rg4y53v64chjys7mbbw89f9-hello-2.10
/nix/store/gdh8165b7rg4y53v64chjys7mbbw89f9-hello-2.10
</syntaxhighlight>
=== Using a binary cache on non-NixOS installations ===
To use a binary cache with a Nix that has been installed on an operating system other than NixOS (e.g. Ubuntu or macOS)  {{ic|/etc/nix/nix.conf}} will need to be edited manually. This can be done by adding something similar to the following lines to {{ic|/etc/nix/nix.conf}}:
<pre>
trusted-public-keys = nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
trusted-substituters = https://nix-community.cachix.org https://cache.nixos.org
trusted-users = root @wheel
</pre>
Note that not all of that information is needed, see the manual for the respective options ([https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-trusted-public-keys trusted-public-keys], [https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-trusted-substituters trusted-substituters], [https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-trusted-users trusted-users]).
With the {{ic|trusted-*}} options set correctly, a user can benefit permanently from a substituter by add the following to their {{ic|~/.config/nix/nix.conf}}
<pre>
substituters = https://nix-community.cachix.org https://cache.nixos.org
</pre>
or temporarily as explained above.
=== Binary cache hint in Flakes ===
You can place a hint to your binary cache in your Flake so when someone builds an output of your Flake, the nix command will ask interactively to trust the specified binary cache.
<syntaxHighlight lang=nix>
{
  nixConfig = {
    extra-substituters = [
      "https://colmena.cachix.org"
    ];
    extra-trusted-public-keys = [
      "colmena.cachix.org-1:7BzpDnjjH8ki2CT3f6GdOk7QAzPOl+1t3LvTLXqYcSg="
    ];
  };
  outputs = { ... }: {
    ...
  };
}
</syntaxHighlight>
=== Binary cache priority ===
Each binary cache has a priority field. A lower number indicates a higher priority.<syntaxhighlight lang="shell-session">
$curl https://cache.nixos.org/nix-cache-info
StoreDir: /nix/store
WantMassQuery: 1
Priority: 40
</syntaxhighlight>You may want to override this value by appending <code>?priority=n</code> at the end of the cache url.<syntaxhighlight lang="nix">
substituters = https://nix-community.cachix.org?priority=1 https://cache.nixos.org?priority=2
</syntaxhighlight>
</syntaxhighlight>


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$ nix copy --to ssh://binarycache.example.com PACKAGE
$ nix copy --to ssh://binarycache.example.com PACKAGE
</syntaxhighlight>
</syntaxhighlight>
For details see the [https://nixos.org/nix/manual/#sec-sharing-packages Sharing Packages Between Machines] in the Nix manual.
For details see the [https://nixos.org/manual/nix/stable/package-management/sharing-packages.html Sharing Packages Between Machines] in the Nix manual.
 
== Signing Existing Packages ==
It is also possible to sign all the packages that already exist in the nix store of the machine serving the binary cache to make them immediately available.
<code>$ nix store sign --extra-experimental-features nix-command --all --key-file /var/cache-priv-key.pem</code>
Note : As of NixOS 24.11 {{ic|--extra-experimental-features nix-command}} is required for {{ic|store sign}} if this is not in your configuration.nix.


== Hosted binary cache ==
== Hosted binary cache ==


https://cachix.org provides hosted binary caches starting with a free plan for public caches.
https://cachix.org provides hosted binary caches starting with a free plan for public caches.
== How to check if content is on a binary cache ==
We can use '''curl''' to check if a binary cache contains a given derivation.
''curl https://cache/store_hash.narinfo''
<syntaxhighlight lang="bash">
$ curl https://fzakaria.cachix.org/949dxjmz632id67hjic04x6f3ljldzxh.narinfo
StorePath: /nix/store/949dxjmz632id67hjic04x6f3ljldzxh-mvn2nix-0.1
URL: nar/4026897ef85219b5b697c1c4ef30d50275423857cb7a81e138c4b1025f550935.nar.xz
Compression: xz
FileHash: sha256:4026897ef85219b5b697c1c4ef30d50275423857cb7a81e138c4b1025f550935
FileSize: 24392
NarHash: sha256:0kk3d8rk82ynqwg8isk83hvq8vszh4354fqg4hhaz40kd49rmm9n
NarSize: 29208
References: 2hhmmj0vbb5d181nfx2mx3p7k54q44ij-apache-maven-3.6.3 6737cq9nvp4k5r70qcgf61004r0l2g3v-bash-4.4-p23 949dxjmz632id67hjic04x6f3ljldzxh-mvn2nix-0.1 hrlxlk768vy5rgl6hc4xiba6gxg6s0yz-mvn2nix-0.1-dependencies qybd7j6v7kb7yhizc7gklgg3lyrxf38y-openjdk-headless-11.0.8+10
Deriver: 585w6p8rclbvz97fwgixvfgnh5493ia2-mvn2nix-0.1.drv
Sig: fzakaria.cachix.org-1:MkOrZCa9qdxHFdE2mtFRsbEzmLUgWGgSrqD3advKfdHLW+SKxj/V2n6+4a/qy6dhCoR+gWQfGzda/jNkER10CQ==
</syntaxhighlight>
Or use ''nix path-info'':
<syntaxhighlight lang="bash">
$ nix path-info -r /nix/store/sb7nbfcc1ca6j0d0v18f7qzwlsyvi8fz-ocaml-4.10.0 --store https://cache.nixos.org/
[0.0 MiB DL] querying libunistring-0.9.10 on https://cache.nixos.org/nix/store/0gc9dr71ldp79cla2qbl3kwdd4ig46pi-linux-headers-5.5
/nix/store/2jysm3dfsgby5sw5jgj43qjrb5v79ms9-bash-4.4-p23
/nix/store/4wy9j24psf9ny4di3anjs7yk2fvfb0gq-glibc-2.31-dev
/nix/store/4z79ipgxqn80ns7mpax25zmb77i3ndfw-gawk-5.1.0
/nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31
/nix/store/czc3c1apx55s37qx4vadqhn3fhikchxi-libunistring-0.9.10
/nix/store/fgn3sih5vi7543jcw389a7qqax8nwkhz-glibc-2.31-bin
/nix/store/sb7nbfcc1ca6j0d0v18f7qzwlsyvi8fz-ocaml-4.10.0
/nix/store/xim9l8hym4iga6d4azam4m0k0p1nw2rm-libidn2-2.3.0
</syntaxhighlight>
Example: Fetch metadata of <code>bash</code>
<pre>
curl https://cache.nixos.org/$(readlink -f $(which bash) | cut -c12-43).narinfo
</pre>
== Command Line Options ==
It is also possible to pass {{ic|substituters}} and {{ic|trusted-public-keys}} on the command line if they are not in {{ic|configuration.nix}} or you want to use a particular binary cache server.
$ nix-build --option substituters "<nowiki>http://binarycache.example.com</nowiki>" --option trusted-public-keys "binarycache.example.com-1:dsafdafDFW123fdasfa123124FADSAD" '<nixpkgs>' -A pkgs.PACKAGE
$ nixos-rebuild --option substituters "<nowiki>http://binarycache.example.com</nowiki>" --option trusted-public-keys "binarycache.example.com-1:dsafdafDFW123fdasfa123124FADSAD" switch
To do an offline install (providing your binary cache contains all the packages required);
$ nixos-install --option substituters "<nowiki>http://binarycache.example.com</nowiki>" --option trusted-public-keys "binarycache.example.com-1:dsafdafDFW123fdasfa123124FADSAD"


== See also ==
== See also ==
<references group="cf."/>
* [https://discourse.nixos.org/t/how-to-use-binary-cache-in-nixos/5202/4 How to use binary cache in NixOS]


<references group="cf."/>
* [https://github.com/zhaofengli/attic attic: Multi-tenant Nix Binary Cache]
 
* [https://discourse.nixos.org/t/nix-binary-cache-for-macos-nix-darwin-with-attic/40118 Nix Binary Cache for MacOS/Nix-Darwin with Attic]
Retrieved from "https://wiki.nixos.org/wiki/Binary_Cache"