Warning: This program is experimental and its interface is subject to change.


nix store copy-log - copy build logs between Nix stores


nix store copy-log [option...] installables...


  • To copy the build log of the hello package from https://cache.nixos.org to the local store:

    # nix store copy-log --from https://cache.nixos.org --eval-store auto nixpkgs#hello

    You can verify that the log is available locally:

    # nix log --substituters '' nixpkgs#hello

    (The flag --substituters '' avoids querying https://cache.nixos.org for the log.)

  • To copy the log for a specific store derivation via SSH:

    # nix store copy-log --to ssh-ng://machine /nix/store/ilgm50plpmcgjhcp33z6n4qbnpqfhxym-glibc-2.33-59.drv


nix store copy-log copies build logs between two Nix stores. The source store is specified using --from and the destination using --to. If one of these is omitted, it defaults to the local store.


  • --debugger
    start an interactive environment if evaluation fails

  • --from store-uri
    URL of the source Nix store.

  • --to store-uri
    URL of the destination Nix store.

Common evaluation options:

  • --arg name expr
    Pass the value expr as the argument name to Nix functions.

  • --argstr name string
    Pass the string string as the argument name to Nix functions.

  • --eval-store store-url
    The Nix store to use for evaluations.

  • --impure
    Allow access to mutable paths and repositories.

  • --include / -I path
    Add path to the list of locations used to look up <...> file names.

  • --override-flake original-ref resolved-ref
    Override the flake registries, redirecting original-ref to resolved-ref.

Common flake-related options:

  • --commit-lock-file
    Commit changes to the flake's lock file.

  • --inputs-from flake-url
    Use the inputs of the specified flake as registry entries.

  • --no-registries
    Don't allow lookups in the flake registries. This option is deprecated; use --no-use-registries.

  • --no-update-lock-file
    Do not allow any updates to the flake's lock file.

  • --no-write-lock-file
    Do not write the flake's newly generated lock file.

  • --override-input input-path flake-url
    Override a specific flake input (e.g. dwarffs/nixpkgs). This implies --no-write-lock-file.

  • --recreate-lock-file
    Recreate the flake's lock file from scratch.

  • --update-input input-path
    Update a specific flake input (ignoring its previous entry in the lock file).

Options that change the interpretation of installables:

  • --derivation
    Operate on the store derivation rather than its outputs.

  • --expr expr
    Interpret installables as attribute paths relative to the Nix expression expr.

  • --file / -f file
    Interpret installables as attribute paths relative to the Nix expression stored in file. If file is the character -, then a Nix expression will be read from standard input. Implies --impure.