pyrox.dev
1# Network Problems {#sec-nix-network-issues}
2
3Nix uses a so-called *binary cache* to optimise building a package from
4source into downloading it as a pre-built binary. That is, whenever a
5command like `nixos-rebuild` needs a path in the Nix store, Nix will try
6to download that path from the Internet rather than build it from
7source. The default binary cache is `https://cache.nixos.org/`. If this
8cache is unreachable, Nix operations may take a long time due to HTTP
9connection timeouts. You can disable the use of the binary cache by
10adding `--option use-binary-caches false`, e.g.
11
12```ShellSession
13# nixos-rebuild switch --option use-binary-caches false
14```
15
16If you have an alternative binary cache at your disposal, you can use it
17instead:
18
19```ShellSession
20# nixos-rebuild switch --option binary-caches http://my-cache.example.org/
21```