---
name: "nix3-why-depends"
section: "1"
platform: "linux"
package: "nix-bin"
version: "2.26.3+dfsg-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/nix3-why-depends"
---

# nix3-why-depends(1)

show why a package has another package in its closure

**Warning** \
 This program is **experimental** ⟨@docroot@/development/experimental-features.md#xp-feature-nix-command⟩ and its interface is subject to change.

## Name

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

## Synopsis

`nix why-depends` \[*option*…\] *package* *dependency*

## Examples

- •

  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
```

- •

  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
```

## Description

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`.

## Options

- •

  `--all` ⟨#opt-all⟩ / `-a`

-

  Show all edges in the dependency graph leading from *package* to *dependency*, rather than just a shortest path.

- •

  `--precise` ⟨#opt-precise⟩

-

  For each edge in the dependency graph, show the files in the parent that cause the dependency.

### Common evaluation options

- •

  `--arg` ⟨#opt-arg⟩ *name* *expr*

-

  Pass the value *expr* as the argument *name* to Nix functions.

- •

  `--arg-from-file` ⟨#opt-arg-from-file⟩ *name* *path*

-

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

- •

  `--arg-from-stdin` ⟨#opt-arg-from-stdin⟩ *name*

-

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

- •

  `--argstr` ⟨#opt-argstr⟩ *name* *string*

-

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

- •

  `--debugger` ⟨#opt-debugger⟩

-

  Start an interactive environment if evaluation fails.

- •

  `--eval-store` ⟨#opt-eval-store⟩ *store-url*

-

  The URL of the Nix store ⟨@docroot@/store/types/index.md#store-url-format⟩ to use for evaluation, i.e. to store derivations (`.drv` files) and inputs referenced by them.

- •

  `--impure` ⟨#opt-impure⟩

-

  Allow access to mutable paths and repositories.

- •

  `--include` ⟨#opt-include⟩ / `-I` *path*

-

  Add *path* to search path entries used to resolve lookup paths ⟨@docroot@/language/constructs/lookup-path.md⟩

-

  This option may be given multiple times.

-

  Paths added through `-I` take precedence over the `nix-path` configuration setting ⟨@docroot@/command-ref/conf-file.md#conf-nix-path⟩ and the `NIX_PATH` environment variable ⟨@docroot@/command-ref/env-common.md#env-NIX\_PATH⟩\\c .

- •

  `--override-flake` ⟨#opt-override-flake⟩ *original-ref* *resolved-ref*

-

  Override the flake registries, redirecting *original-ref* to *resolved-ref*.

### Common flake-related options

- •

  `--commit-lock-file` ⟨#opt-commit-lock-file⟩

-

  Commit changes to the flake’s lock file.

- •

  `--inputs-from` ⟨#opt-inputs-from⟩ *flake-url*

-

  Use the inputs of the specified flake as registry entries.

- •

  `--no-registries` ⟨#opt-no-registries⟩

-

  Don’t allow lookups in the flake registries.

  -

    **DEPRECATED**

  -

    Use `--no-use-registries` ⟨@docroot@/command-ref/conf-file.md#conf-use-registries⟩ instead.

- •

  `--no-update-lock-file` ⟨#opt-no-update-lock-file⟩

-

  Do not allow any updates to the flake’s lock file.

- •

  `--no-write-lock-file` ⟨#opt-no-write-lock-file⟩

-

  Do not write the flake’s newly generated lock file.

- •

  `--output-lock-file` ⟨#opt-output-lock-file⟩ *flake-lock-path*

-

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

- •

  `--override-input` ⟨#opt-override-input⟩ *input-path* *flake-url*

-

  Override a specific flake input (e.g. `dwarffs/nixpkgs`). This implies `--no-write-lock-file`.

- •

  `--recreate-lock-file` ⟨#opt-recreate-lock-file⟩

-

  Recreate the flake’s lock file from scratch.

  -

    **DEPRECATED**

  -

    Use `nix flake update` ⟨@docroot@/command-ref/new-cli/nix3-flake-update.md⟩ instead.

- •

  `--reference-lock-file` ⟨#opt-reference-lock-file⟩ *flake-lock-path*

-

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

- •

  `--update-input` ⟨#opt-update-input⟩ *input-path*

-

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

  -

    **DEPRECATED**

  -

    Use `nix flake update` ⟨@docroot@/command-ref/new-cli/nix3-flake-update.md⟩ instead.

### Logging-related options

- •

  `--debug` ⟨#opt-debug⟩

-

  Set the logging verbosity level to ‘debug’.

- •

  `--log-format` ⟨#opt-log-format⟩ *format*

-

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

- •

  `--print-build-logs` ⟨#opt-print-build-logs⟩ / `-L`

-

  Print full build logs on standard error.

- •

  `--quiet` ⟨#opt-quiet⟩

-

  Decrease the logging verbosity level.

- •

  `--verbose` ⟨#opt-verbose⟩ / `-v`

-

  Increase the logging verbosity level.

### Miscellaneous global options

- •

  `--help` ⟨#opt-help⟩

-

  Show usage information.

- •

  `--offline` ⟨#opt-offline⟩

-

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

- •

  `--option` ⟨#opt-option⟩ *name* *value*

-

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

- •

  `--refresh` ⟨#opt-refresh⟩

-

  Consider all previously downloaded files out-of-date.

- •

  `--repair` ⟨#opt-repair⟩

-

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

- •

  `--version` ⟨#opt-version⟩

-

  Show version information.

### Options that change the interpretation of **installables**

- •

  `--derivation` ⟨#opt-derivation⟩

-

  Operate on the store derivation ⟨@docroot@/glossary.md#gloss-store-derivation⟩ rather than its outputs.

- •

  `--expr` ⟨#opt-expr⟩ *expr*

-

  Interpret *installables* ⟨@docroot@/command-ref/new-cli/nix.md#installables⟩ as attribute paths relative to the Nix expression *expr*.

- •

  `--file` ⟨#opt-file⟩ / `-f` *file*

-

  Interpret *installables* ⟨@docroot@/command-ref/new-cli/nix.md#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` ⟨@docroot@/command-ref/conf-file.md#command-line-flags⟩ for overriding configuration settings with command line flags.