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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:

    $ nix-env --install --attr nixpkgs.nix-serve

You can then start the server, listening for HTTP connections on whatever port you like:

    $ nix-serve -p 8080

To check whether it works, try the following on the client:

    $ curl http://avalon:8080/nix-cache-info

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 `--substituters`, e.g.:

    $ nix-env --install --attr nixpkgs.firefox --substituters http://avalon:8080/

The option `substituters` 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:

    substituters = http://avalon:8080/ https://cache.nixos.org/