Name

nix-env - manipulate or query Nix user environments

Synopsis

nix-env operation [options] [arguments…] [--option name value] [--arg name value] [--argstr name value] [{--file | -f} path] [{--profile | -p} path] [--system-filter system] [--dry-run]

Description

The command nix-env is used to manipulate Nix user environments. User environments are sets of software packages available to a user at some point in time. In other words, they are a synthesised view of the programs available in the Nix store. There may be many user environments: different users can have different environments, and individual users can switch between different environments.

nix-env takes exactly one operation flag which indicates the subcommand to be performed. The following operations are available:

These pages can be viewed offline:

  • man nix-env-<operation>.

    Example: man nix-env-install

  • nix-env --help --<operation>

    Example: nix-env --help --install

Package sources

nix-env can obtain packages from multiple sources:

  • An attribute set of derivations from:
    • The default Nix expression (by default)
    • A Nix file, specified via --file
    • A profile, specified via --from-profile
    • A Nix expression that is a function which takes default expression as argument, specified via --from-expression
  • A store path

Selectors

Several operations, such as nix-env --query and nix-env --install, take a list of arguments that specify the packages on which to operate.

Packages are identified based on a name part and a version part of a symbolic derivation name:

  • name: Everything up to but not including the first dash (-) that is not followed by a letter.
  • version: The rest, excluding the separating dash.

Example

nix-env parses the symbolic derivation name apache-httpd-2.0.48 as:

{
  "name": "apache-httpd",
  "version": "2.0.48"
}

Example

nix-env parses the symbolic derivation name firefox.* as:

{
  "name": "firefox.*",
  "version": ""
}

The name parts of the arguments to nix-env are treated as extended regular expressions and matched against the name parts of derivation names in the package source. The match is case-sensitive. The regular expression can optionally be followed by a dash (-) and a version number; if omitted, any version of the package will match. For details on regular expressions, see regex(7).

Example

Common patterns for finding package names with nix-env:

  • firefox

    Matches the package name firefox and any version.

  • firefox-32.0

    Matches the package name firefox and version 32.0.

  • gtk\\+

    Matches the package name gtk+. The + character must be escaped using a backslash (\) to prevent it from being interpreted as a quantifier, and the backslash must be escaped in turn with another backslash to ensure that the shell passes it on.

  • .\*

    Matches any package name. This is the default for most commands.

  • '.*zip.*'

    Matches any package name containing the string zip. Note the dots: '*zip*' does not work, because in a regular expression, the character * is interpreted as a quantifier.

  • '.*(firefox|chromium).*'

    Matches any package name containing the strings firefox or chromium.

Files

nix-env operates on the following files.

Default Nix expression

The source for the Nix expressions used by nix-env by default:

It is loaded as follows:

  • If the default expression is a file, it is loaded as a Nix expression.
  • If the default expression is a directory containing a default.nix file, that default.nix file is loaded as a Nix expression.
  • If the default expression is a directory without a default.nix file, then its contents (both files and subdirectories) are loaded as Nix expressions. The expressions are combined into a single attribute set, each expression under an attribute with the same name as the original file or subdirectory. Subdirectories without a default.nix file are traversed recursively in search of more Nix expressions, but the names of these intermediate directories are not added to the attribute paths of the default Nix expression.

Then, the resulting expression is interpreted like this:

  • If the expression is an attribute set, it is used as the default Nix expression.
  • If the expression is a function, an empty set is passed as argument and the return value is used as the default Nix expression.

Example

If the default expression contains two files, foo.nix and bar.nix, then the default Nix expression will be equivalent to

{
  foo = import ~/.nix-defexpr/foo.nix;
  bar = import ~/.nix-defexpr/bar.nix;
}

The file manifest.nix is always ignored.

The command nix-channel places a symlink to the current user's channels in this directory, the user channel link. This makes all subscribed channels available as attributes in the default expression.

A symlink that ensures that nix-env can find the current user's channels:

This symlink points to:

  • $XDG_STATE_HOME/profiles/channels for regular users
  • $NIX_STATE_DIR/profiles/per-user/root/channels for root

In a multi-user installation, you may also have ~/.nix-defexpr/channels_root, which links to the channels of the root user.

Profiles

A directory that contains links to profiles managed by nix-env and nix profile:

  • $XDG_STATE_HOME/nix/profiles for regular users
  • $NIX_STATE_DIR/profiles/per-user/root if the user is root

A profile is a directory of symlinks to files in the Nix store.

Filesystem layout

Profiles are versioned as follows. When using a profile named path, path is a symlink to path-N-link, where N is the version of the profile. In turn, path-N-link is a symlink to a path in the Nix store. For example:

$ ls -l ~alice/.local/state/nix/profiles/profile*
lrwxrwxrwx 1 alice users 14 Nov 25 14:35 /home/alice/.local/state/nix/profiles/profile -> profile-7-link
lrwxrwxrwx 1 alice users 51 Oct 28 16:18 /home/alice/.local/state/nix/profiles/profile-5-link -> /nix/store/q69xad13ghpf7ir87h0b2gd28lafjj1j-profile
lrwxrwxrwx 1 alice users 51 Oct 29 13:20 /home/alice/.local/state/nix/profiles/profile-6-link -> /nix/store/6bvhpysd7vwz7k3b0pndn7ifi5xr32dg-profile
lrwxrwxrwx 1 alice users 51 Nov 25 14:35 /home/alice/.local/state/nix/profiles/profile-7-link -> /nix/store/mp0x6xnsg0b8qhswy6riqvimai4gm677-profile

Each of these symlinks is a root for the Nix garbage collector.

The contents of the store path corresponding to each version of the profile is a tree of symlinks to the files of the installed packages, e.g.

$ ll -R ~eelco/.local/state/nix/profiles/profile-7-link/
/home/eelco/.local/state/nix/profiles/profile-7-link/:
total 20
dr-xr-xr-x 2 root root 4096 Jan  1  1970 bin
-r--r--r-- 2 root root 1402 Jan  1  1970 manifest.nix
dr-xr-xr-x 4 root root 4096 Jan  1  1970 share

/home/eelco/.local/state/nix/profiles/profile-7-link/bin:
total 20
lrwxrwxrwx 5 root root 79 Jan  1  1970 chromium -> /nix/store/ijm5k0zqisvkdwjkc77mb9qzb35xfi4m-chromium-86.0.4240.111/bin/chromium
lrwxrwxrwx 7 root root 87 Jan  1  1970 spotify -> /nix/store/w9182874m1bl56smps3m5zjj36jhp3rn-spotify-1.1.26.501.gbe11e53b-15/bin/spotify
lrwxrwxrwx 3 root root 79 Jan  1  1970 zoom-us -> /nix/store/wbhg2ga8f3h87s9h5k0slxk0m81m4cxl-zoom-us-5.3.469451.0927/bin/zoom-us

/home/eelco/.local/state/nix/profiles/profile-7-link/share/applications:
total 12
lrwxrwxrwx 4 root root 120 Jan  1  1970 chromium-browser.desktop -> /nix/store/4cf803y4vzfm3gyk3vzhzb2327v0kl8a-chromium-unwrapped-86.0.4240.111/share/applications/chromium-browser.desktop
lrwxrwxrwx 7 root root 110 Jan  1  1970 spotify.desktop -> /nix/store/w9182874m1bl56smps3m5zjj36jhp3rn-spotify-1.1.26.501.gbe11e53b-15/share/applications/spotify.desktop
lrwxrwxrwx 3 root root 107 Jan  1  1970 us.zoom.Zoom.desktop -> /nix/store/wbhg2ga8f3h87s9h5k0slxk0m81m4cxl-zoom-us-5.3.469451.0927/share/applications/us.zoom.Zoom.desktop

…

Each profile version contains a manifest file:

A symbolic link to the user's current profile:

By default, this symlink points to:

  • $XDG_STATE_HOME/nix/profiles/profile for regular users
  • $NIX_STATE_DIR/profiles/per-user/root/profile for root

The PATH environment variable should include /bin subdirectory of the profile link (e.g. ~/.nix-profile/bin) for the user environment to be visible to the user. The installer sets this up by default, unless you enable use-xdg-base-directories.