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 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.

       •  --arg-from-file name path

          Pass the contents of file path as the argument name to Nix functions.

       •  --arg-from-stdin name

          Pass the contents of stdin as the argument name to Nix functions.

       •  --argstr name string

          Pass the string string as the argument name to Nix functions.

       •  --debugger

          Start an interactive environment if evaluation fails.

       •  --eval-store store-url

          The  URL of the Nix store  to  use  for  evaluation, i.e. to store derivations (.drv files) and inputs
          referenced by them.

       •  --impure

          Allow access to mutable paths and repositories.

       •  --include / -I path

          Add path to search path entries used to resolve lookup paths

          This option may be given multiple times.

          Paths added through -I take  precedence  over  the  nix-path configuration setting  and  the  NIX_PATH
          environment variable.

       •  --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.

                 DEPRECATED

                 Use --no-use-registries instead.

       •  --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.

       •  --output-lock-file flake-lock-path

          Write the given lock file instead of flake.lock within the top-level flake.

       •  --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.

                 DEPRECATED

                 Use nix flake update instead.

       •  --reference-lock-file flake-lock-path

          Read the given lock file instead of flake.lock within the top-level flake.

       •  --update-input input-path

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

                 DEPRECATED

                 Use nix flake update instead.

   Logging-related options
       •  --debug

          Set the logging verbosity level to ‘debug’.

       •  --log-format format

          Set the format of log output; one of raw, internal-json, bar or bar-with-logs.

       •  --print-build-logs / -L

          Print full build logs on standard error.

       •  --quiet

          Decrease the logging verbosity level.

       •  --verbose / -v

          Increase the logging verbosity level.

   Miscellaneous global options
       •  --help

          Show usage information.

       •  --offline

          Disable substituters and consider all previously downloaded files up-to-date.

       •  --option name value

          Set the Nix configuration setting name to value (overriding nix.conf).

       •  --refresh

          Consider all previously downloaded files out-of-date.

       •  --repair

          During  evaluation,  rewrite  missing  or  corrupted  files in the Nix store. During building, rebuild
          missing or corrupted store paths.

       •  --version

          Show version information.

   Options that change the interpretation of installables
       •  --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.

          Note

          See man nix.conf for overriding configuration settings with command line flags.

                                                                                                     nix3-log(1)