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nix3-why-depends(1) General Commands Manual nix3-why-depends(1)

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


nix why-depends - show why a package has another package in its closure


nix why-depends [option…] package dependency


Show one path through the dependency graph leading from Hello to Glibc:

# nix why-depends nixpkgs#hello nixpkgs#glibc
└───bin/hello: …...................../nix/store/9l06v7fc38c1x3r2iydl15ksgz0ysb82-glibc-2.32/lib/ld-linux-x86-64.…

→ /nix/store/9l06v7fc38c1x3r2iydl15ksgz0ysb82-glibc-2.32
Show all files and paths in the dependency graph leading from Thunderbird to libX11:

# nix why-depends --all nixpkgs#thunderbird nixpkgs#xorg.libX11
├───lib/thunderbird/ …6wrw-libxcb-1.14/lib:/nix/store/adzfjjh8w25vdr0xdx9x16ah4f5rqrw5-libX11-1.7.0/lib:/nix/store/ssf…
│   → /nix/store/adzfjjh8w25vdr0xdx9x16ah4f5rqrw5-libX11-1.7.0
├───lib/thunderbird/ …pxyc-libXt-1.2.0/lib:/nix/store/1qj29ipxl2fyi2b13l39hdircq17gnk0-libXdamage-1.1.5/lib:/nix/store…
│   → /nix/store/1qj29ipxl2fyi2b13l39hdircq17gnk0-libXdamage-1.1.5
│   ├───lib/ …-libXfixes-5.0.3/lib:/nix/store/adzfjjh8w25vdr0xdx9x16ah4f5rqrw5-libX11-1.7.0/lib:/nix/store/9l0…
│   │   → /nix/store/adzfjjh8w25vdr0xdx9x16ah4f5rqrw5-libX11-1.7.0
Show why Glibc depends on itself:

# nix why-depends nixpkgs#glibc nixpkgs#glibc
└───lib/ …che       Do not use /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31/etc/  --…

→ /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31
Show why Geeqie has a build-time dependency on systemd:

# nix why-depends --derivation nixpkgs#geeqie nixpkgs#systemd
└───/: …atch.drv",["out"]),("/nix/store/qzh8dyq3lfbk3i1acbp7x9wh3il2imiv-gtk+3-3.24.21.drv",["dev"]),("/…

→ /nix/store/qzh8dyq3lfbk3i1acbp7x9wh3il2imiv-gtk+3-3.24.21.drv
└───/: …16.0.drv",["dev"]),("/nix/store/8kp79fyslf3z4m3dpvlh6w46iaadz5c2-cups-2.3.3.drv",["dev"]),("/nix…
→ /nix/store/8kp79fyslf3z4m3dpvlh6w46iaadz5c2-cups-2.3.3.drv
└───/: ….3.1.drv",["out"]),("/nix/store/yd3ihapyi5wbz1kjacq9dbkaq5v5hqjg-systemd-246.4.drv",["dev"]),("/…
→ /nix/store/yd3ihapyi5wbz1kjacq9dbkaq5v5hqjg-systemd-246.4.drv


Nix automatically determines potential runtime dependencies between store paths by scanning for the hash parts of store paths. For instance, if there exists a store path /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31, and a file inside another store path contains the string 9df65igw…, then the latter store path refers to the former, and thus might need it at runtime. Nix always maintains the existence of the transitive closure of a store path under the references relationship; it is therefore not possible to install a store path without having all of its references present.

Sometimes Nix packages end up with unexpected runtime dependencies; for instance, a reference to a compiler might accidentally end up in a binary, causing the former to be in the latter’s closure. This kind of closure size bloat is undesirable.

nix why-depends allows you to diagnose the cause of such issues. It shows why the store path package depends on the store path dependency, by showing a shortest sequence in the references graph from the former to the latter. Also, for each node along this path, it shows a file fragment containing a reference to the next store path in the sequence.

To show why derivation package has a build-time rather than runtime dependency on derivation dependency, use --derivation.


  • --all / -a
    Show all edges in the dependency graph leading from package to dependency, rather than just a shortest path.
  • --precise
    For each edge in the dependency graph, show the files in the parent that cause the dependency.

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.