lix/doc/manual/src/package-management/binary-cache-substituter.md

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# Serving a Nix store via HTTP
You can easily share the Nix store of a machine via HTTP. This allows
other machines to fetch store paths from that machine to speed up
installations. It uses the same *binary cache* mechanism that Nix
usually uses to fetch pre-built binaries from <https://cache.nixos.org>.
The daemon that handles binary cache requests via HTTP, `nix-serve`, is
not part of the Nix distribution, but you can install it from Nixpkgs:
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```console
$ nix-env -i nix-serve
```
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You can then start the server, listening for HTTP connections on
whatever port you like:
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```console
$ nix-serve -p 8080
```
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To check whether it works, try the following on the client:
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```console
$ curl http://avalon:8080/nix-cache-info
```
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which should print something like:
StoreDir: /nix/store
WantMassQuery: 1
Priority: 30
On the client side, you can tell Nix to use your binary cache using
`--option extra-binary-caches`, e.g.:
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```console
$ nix-env -i firefox --option extra-binary-caches http://avalon:8080/
```
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The option `extra-binary-caches` tells Nix to use this binary cache in
addition to your default caches, such as <https://cache.nixos.org>.
Thus, for any path in the closure of Firefox, Nix will first check if
the path is available on the server `avalon` or another binary caches.
If not, it will fall back to building from source.
You can also tell Nix to always use your binary cache by adding a line
to the `nix.conf` configuration file like this:
binary-caches = http://avalon:8080/ https://cache.nixos.org/