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2 xmlns:xlink="http://www.w3.org/1999/xlink"
3 xmlns:xi="http://www.w3.org/2001/XInclude"
4 version="5.0"
5 xml:id="sec-nix-store-corruption">
6 <title>Nix Store Corruption</title>
7
8 <para>
9 After a system crash, it’s possible for files in the Nix store to become
10 corrupted. (For instance, the Ext4 file system has the tendency to replace
11 un-synced files with zero bytes.) NixOS tries hard to prevent this from
12 happening: it performs a <command>sync</command> before switching to a new
13 configuration, and Nix’s database is fully transactional. If corruption
14 still occurs, you may be able to fix it automatically.
15 </para>
16
17 <para>
18 If the corruption is in a path in the closure of the NixOS system
19 configuration, you can fix it by doing
20<screen>
21# nixos-rebuild switch --repair
22</screen>
23 This will cause Nix to check every path in the closure, and if its
24 cryptographic hash differs from the hash recorded in Nix’s database, the
25 path is rebuilt or redownloaded.
26 </para>
27
28 <para>
29 You can also scan the entire Nix store for corrupt paths:
30<screen>
31# nix-store --verify --check-contents --repair
32</screen>
33 Any corrupt paths will be redownloaded if they’re available in a binary
34 cache; otherwise, they cannot be repaired.
35 </para>
36</section>