2014-08-24 18:18:18 +01:00
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="sec-nix-store-corruption">
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<title>Nix Store Corruption</title>
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<para>After a system crash, it’s possible for files in the Nix store
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to become corrupted. (For instance, the Ext4 file system has the
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tendency to replace un-synced files with zero bytes.) NixOS tries
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hard to prevent this from happening: it performs a
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<command>sync</command> before switching to a new configuration, and
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Nix’s database is fully transactional. If corruption still occurs,
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you may be able to fix it automatically.</para>
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<para>If the corruption is in a path in the closure of the NixOS
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system configuration, you can fix it by doing
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<screen>
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2016-06-01 15:23:32 +01:00
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# nixos-rebuild switch --repair
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2014-08-24 18:18:18 +01:00
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</screen>
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This will cause Nix to check every path in the closure, and if its
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cryptographic hash differs from the hash recorded in Nix’s database,
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the path is rebuilt or redownloaded.</para>
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<para>You can also scan the entire Nix store for corrupt paths:
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<screen>
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2016-06-01 15:23:32 +01:00
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# nix-store --verify --check-contents --repair
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2014-08-24 18:18:18 +01:00
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</screen>
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Any corrupt paths will be redownloaded if they’re available in a
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binary cache; otherwise, they cannot be repaired.</para>
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2016-06-01 15:23:32 +01:00
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</section>
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