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

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Show one path through the dependency graph leading from Hello to Glibc:
# nix why-depends nixpkgs#hello nixpkgs#glibc
/nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10
└───bin/hello: …...................../nix/store/9l06v7fc38c1x3r2iydl15ksgz0ysb82-glibc-2.32/lib/ld-linux-x86-64.…
  → /nix/store/9l06v7fc38c1x3r2iydl15ksgz0ysb82-glibc-2.32
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Show all files and paths in the dependency graph leading from Thunderbird to libX11:
# nix why-depends --all nixpkgs#thunderbird nixpkgs#xorg.libX11
/nix/store/qfc8729nzpdln1h0hvi1ziclsl3m84sr-thunderbird-78.5.1
├───lib/thunderbird/libxul.so: …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/libxul.so: …pxyc-libXt-1.2.0/lib:/nix/store/1qj29ipxl2fyi2b13l39hdircq17gnk0-libXdamage-1.1.5/lib:/nix/store…
│   → /nix/store/1qj29ipxl2fyi2b13l39hdircq17gnk0-libXdamage-1.1.5
│   ├───lib/libXdamage.so.1.1.0: …-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
/nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31
└───lib/ld-2.31.so: …che       Do not use /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31/etc/ld.so.cache.  --…
  → /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31
•
Show why Geeqie has a build-time dependency on systemd:
# nix why-depends --derivation nixpkgs#geeqie nixpkgs#systemd
/nix/store/drrpq2fqlrbj98bmazrnww7hm1in3wgj-geeqie-1.4.drv
└───/: …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.

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

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--arg name expr
Pass the value expr as the argument name to Nix functions.
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--arg-from-file name path
Pass the contents of file path as the argument name to Nix functions.
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--arg-from-stdin name
Pass the contents of stdin as the argument name to Nix functions.
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--argstr name string
Pass the string string as the argument name to Nix functions.
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--debugger
Start an interactive environment if evaluation fails.
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--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.
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--impure
Allow access to mutable paths and repositories.
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--include / -I path
Add path to the Nix search path. The Nix search path is initialized from the colon-separated NIX_PATH environment variable, and is used to look up the location of Nix expressions using paths enclosed in angle brackets (i.e., <nixpkgs>).
For instance, passing
-I /home/eelco/Dev
-I /etc/nixos
will cause Nix to look for paths relative to /home/eelco/Dev and /etc/nixos, in that order. This is equivalent to setting the NIX_PATH environment variable to
/home/eelco/Dev:/etc/nixos
It is also possible to match paths against a prefix. For example, passing
-I nixpkgs=/home/eelco/Dev/nixpkgs-branch
-I /etc/nixos
will cause Nix to search for <nixpkgs/path> in /home/eelco/Dev/nixpkgs-branch/path and /etc/nixos/nixpkgs/path.
If a path in the Nix search path starts with http:// or https://, it is interpreted as the URL of a tarball that will be downloaded and unpacked to a temporary location. The tarball must consist of a single top-level directory. For example, passing
-I nixpkgs=https://github.com/NixOS/nixpkgs/archive/master.tar.gz
tells Nix to download and use the current contents of the master branch in the nixpkgs repository.
The URLs of the tarballs from the official nixos.org channels (see the manual page for nix-channel) can be abbreviated as channel:<channel-name>. For instance, the following two flags are equivalent:
-I nixpkgs=channel:nixos-21.05
-I nixpkgs=https://nixos.org/channels/nixos-21.05/nixexprs.tar.xz
You can also fetch source trees using flake URLs and add them to the search path. For instance,
-I nixpkgs=flake:nixpkgs
specifies that the prefix nixpkgs shall refer to the source tree downloaded from the nixpkgs entry in the flake registry. Similarly,
-I nixpkgs=flake:github:NixOS/nixpkgs/nixos-22.05
makes <nixpkgs> refer to a particular branch of the NixOS/nixpkgs repository on GitHub.
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--override-flake original-ref resolved-ref
Override the flake registries, redirecting original-ref to resolved-ref.
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--commit-lock-file
Commit changes to the flake’s lock file.
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--inputs-from flake-url
Use the inputs of the specified flake as registry entries.
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--no-registries
Don’t allow lookups in the flake registries.
DEPRECATED
Use --no-use-registries instead.
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--no-update-lock-file
Do not allow any updates to the flake’s lock file.
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--no-write-lock-file
Do not write the flake’s newly generated lock file.
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--output-lock-file flake-lock-path
Write the given lock file instead of flake.lock within the top-level flake.
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--override-input input-path flake-url
Override a specific flake input (e.g. dwarffs/nixpkgs). This implies --no-write-lock-file.
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--recreate-lock-file
Recreate the flake’s lock file from scratch.
DEPRECATED
Use nix flake update instead.
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--reference-lock-file flake-lock-path
Read the given lock file instead of flake.lock within the top-level flake.
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--update-input input-path
Update a specific flake input (ignoring its previous entry in the lock file).
DEPRECATED
Use nix flake update instead.
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--debug
Set the logging verbosity level to ‘debug’.
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--log-format format
Set the format of log output; one of raw, internal-json, bar or bar-with-logs.
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--print-build-logs / -L
Print full build logs on standard error.
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--quiet
Decrease the logging verbosity level.
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--verbose / -v
Increase the logging verbosity level.

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--help
Show usage information.
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--offline
Disable substituters and consider all previously downloaded files up-to-date.
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--option name value
Set the Nix configuration setting name to value (overriding nix.conf).
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--refresh
Consider all previously downloaded files out-of-date.
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--repair
During evaluation, rewrite missing or corrupted files in the Nix store. During building, rebuild missing or corrupted store paths.
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--version
Show version information.

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--derivation
Operate on the store derivation rather than its outputs.
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--expr expr
Interpret installables as attribute paths relative to the Nix expression expr.
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--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.