nix-super/doc/manual/src/command-ref/nix-store/verify.md

# Name

`nix-store --verify` - check Nix database for consistency

# Synopsis

`nix-store` `--verify` [`--check-contents`] [`--repair`]

# Description

The operation `--verify` verifies the internal consistency of the Nix
database, and the consistency between the Nix database and the Nix
store. Any inconsistencies encountered are automatically repaired.
Inconsistencies are generally the result of the Nix store or database
being modified by non-Nix tools, or of bugs in Nix itself.

This operation has the following options:

  - `--check-contents`

    Checks that the contents of every valid store path has not been
    altered by computing a SHA-256 hash of the contents and comparing it
    with the hash stored in the Nix database at build time. Paths that
    have been modified are printed out. For large stores,
    `--check-contents` is obviously quite slow.

  - `--repair`

    If any valid path is missing from the store, or (if
    `--check-contents` is given) the contents of a valid path has been
    modified, then try to repair the path by redownloading it. See
    `nix-store --repair-path` for details.

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