nix log

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

# Name

`nix log` - show the build log of the specified packages or paths, if available

# Synopsis

`nix log` [option...] installable

# Examples

- Get the build log of GNU Hello:

      # nix log nixpkgs#hello

- Get the build log of a specific store path:

      # nix log /nix/store/lmngj4wcm9rkv3w4dfhzhcyij3195hiq-thunderbird-52.2.1

- Get a build log from a specific binary cache:

      # nix log --store https://cache.nixos.org nixpkgs#hello

# Description

This command prints the log of a previous build of the derivation installable on standard output.

Nix looks for build logs in two places:

- In the directory `/nix/var/log/nix/drvs`, which contains logs for locally built derivations.

- In the binary caches listed in the `substituters` setting. Logs should be named `<cache>/log/<base-name-of-store-path>`, where `store-path` is a derivation, e.g. `https://cache.nixos.org/log/dvmig8jgrdapvbyxb1rprckdmdqx08kv-hello-2.10.drv`. For non-derivation store paths, Nix will first try to determine the deriver by fetching the `.narinfo` file for this store path.

# Options

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.