.\" -*- mode: troff; coding: utf-8 -*-
.TH "nix3-why-depends" "1" ""
.PP
\fBWarning\fR: This program is \fBexperimental\fR and its interface is subject to change.
.SH Name
\fCnix why-depends\fR - show why a package has another package in its closure
.SH Synopsis
\fCnix why-depends\fR [\fIoption\fR\[u2026]] \fIpackage\fR \fIdependency\fR
.SH Examples
.IP "\(bu" 2
Show one path through the dependency graph leading from Hello to
Glibc:
.LP
.EX
# 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
.EE
.IP "\(bu" 2
Show all files and paths in the dependency graph leading from
Thunderbird to libX11:
.LP
.EX
# 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
…
.EE
.IP "\(bu" 2
Show why Glibc depends on itself:
.LP
.EX
# 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
.EE
.IP "\(bu" 2
Show why Geeqie has a build-time dependency on \fCsystemd\fR:
.LP
.EX
# nix why-depends --derivation nixpkgs#geeqie nixpkgs#systemd
/nix/store/drrpq2fqlrbj98bmazrnww7hm1in3wgj-geeqie-1.4.drv
└───/: …atch.drv\(dq,[\(dqout\(dq]),(\(dq/nix/store/qzh8dyq3lfbk3i1acbp7x9wh3il2imiv-gtk+3-3.24.21.drv\(dq,[\(dqdev\(dq]),(\(dq/…
  → /nix/store/qzh8dyq3lfbk3i1acbp7x9wh3il2imiv-gtk+3-3.24.21.drv
  └───/: …16.0.drv\(dq,[\(dqdev\(dq]),(\(dq/nix/store/8kp79fyslf3z4m3dpvlh6w46iaadz5c2-cups-2.3.3.drv\(dq,[\(dqdev\(dq]),(\(dq/nix…
      → /nix/store/8kp79fyslf3z4m3dpvlh6w46iaadz5c2-cups-2.3.3.drv
      └───/: ….3.1.drv\(dq,[\(dqout\(dq]),(\(dq/nix/store/yd3ihapyi5wbz1kjacq9dbkaq5v5hqjg-systemd-246.4.drv\(dq,[\(dqdev\(dq]),(\(dq/…
          → /nix/store/yd3ihapyi5wbz1kjacq9dbkaq5v5hqjg-systemd-246.4.drv
.EE
.SH Description
Nix automatically determines potential runtime dependencies between
store paths by scanning for the \fIhash parts\fR of store paths. For
instance, if there exists a store path
\fC/nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31\fR, and a file
inside another store path contains the string \fC9df65igw…\fR, then the
latter store path \fIrefers\fR 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.
.PP
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\[u2019]s closure. This kind of
\fIclosure size bloat\fR is undesirable.
.PP
\fCnix why-depends\fR allows you to diagnose the cause of such issues. It
shows why the store path \fIpackage\fR depends on the store path
\fIdependency\fR, 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.
.PP
To show why derivation \fIpackage\fR has a build-time rather than runtime
dependency on derivation \fIdependency\fR, use \fC--derivation\fR.
.SH Options
.IP "\(bu" 2
\fC--all\fR / \fC-a\fR
.br
Show all edges in the dependency graph leading from \fIpackage\fR to \fIdependency\fR, rather than just a shortest path.
.IP "\(bu" 2
\fC--precise\fR
.br
For each edge in the dependency graph, show the files in the parent that cause the dependency.
.LP
\fBCommon evaluation options:\fR
.IP "\(bu" 2
\fC--arg\fR \fIname\fR \fIexpr\fR
.br
Pass the value \fIexpr\fR as the argument \fIname\fR to Nix functions.
.IP "\(bu" 2
\fC--argstr\fR \fIname\fR \fIstring\fR
.br
Pass the string \fIstring\fR as the argument \fIname\fR to Nix functions.
.IP "\(bu" 2
\fC--eval-store\fR \fIstore-url\fR
.br
The Nix store to use for evaluations.
.IP "\(bu" 2
\fC--impure\fR
.br
Allow access to mutable paths and repositories.
.IP "\(bu" 2
\fC--include\fR / \fC-I\fR \fIpath\fR
.br
Add \fIpath\fR to the list of locations used to look up \fC<...>\fR file names.
.IP "\(bu" 2
\fC--override-flake\fR \fIoriginal-ref\fR \fIresolved-ref\fR
.br
Override the flake registries, redirecting \fIoriginal-ref\fR to \fIresolved-ref\fR.
.LP
\fBCommon flake-related options:\fR
.IP "\(bu" 2
\fC--commit-lock-file\fR
.br
Commit changes to the flake\[u2019]s lock file.
.IP "\(bu" 2
\fC--inputs-from\fR \fIflake-url\fR
.br
Use the inputs of the specified flake as registry entries.
.IP "\(bu" 2
\fC--no-registries\fR
.br
Don\[u2019]t allow lookups in the flake registries. This option is deprecated; use \fC--no-use-registries\fR.
.IP "\(bu" 2
\fC--no-update-lock-file\fR
.br
Do not allow any updates to the flake\[u2019]s lock file.
.IP "\(bu" 2
\fC--no-write-lock-file\fR
.br
Do not write the flake\[u2019]s newly generated lock file.
.IP "\(bu" 2
\fC--override-input\fR \fIinput-path\fR \fIflake-url\fR
.br
Override a specific flake input (e.g. \fCdwarffs/nixpkgs\fR). This implies \fC--no-write-lock-file\fR.
.IP "\(bu" 2
\fC--recreate-lock-file\fR
.br
Recreate the flake\[u2019]s lock file from scratch.
.IP "\(bu" 2
\fC--update-input\fR \fIinput-path\fR
.br
Update a specific flake input (ignoring its previous entry in the lock file).
.LP
\fBOptions that change the interpretation of installables:\fR
.IP "\(bu" 2
\fC--derivation\fR
.br
Operate on the store derivation rather than its outputs.
.IP "\(bu" 2
\fC--expr\fR \fIexpr\fR
.br
Interpret installables as attribute paths relative to the Nix expression \fIexpr\fR.
.IP "\(bu" 2
\fC--file\fR / \fC-f\fR \fIfile\fR
.br
Interpret installables as attribute paths relative to the Nix expression stored in \fIfile\fR. If \fIfile\fR is the character -, then a Nix expression will be read from standard input.