nix-mirror: a tool for mirroring nix binary caches

Background

It is possible to mirror a nix binary cache using the nix command line tool using a command sucn as:

xzcat store-paths.xz | nix copy --from https://cache.nixos.org --to file:///path/to/where/the/mirror/should/end/up

where store-paths.xz is a file containing the store-paths of all binaries in the cache, e.g. https://channels.nixos.org/nixos-unstable/store-paths.xz

However that command will use a lot of system resources since it will unpack all of the downloaded files and repack them before writing them to disk (if I have understood the reasons for the high cpu usage correctly).

Features

• Parallel downloads
• Atomic downloads
• Sha256 verification of downloaded archives.

Building

With cargo

Make sure to have openssl and pkg-config installed and run cargo build. If using nix you can use the provided shell.nix which is only a symlink to default.nix to get the dependencies.

With nix

Run nix-build as usual.

Usage

• nix-mirror --help to show application help
• nix-mirror store-paths.xz ./mirror to download all the archives in store-paths.xz and their transitive dependencies to the directory ./mirror.

License

Licensed under either of

• Apache License, Version 2.0
• MIT license

at your option.