nix-env

# Name

`nix-env` - manipulate or query Nix user environments

# Synopsis

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

# 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. These are documented below.

# Selectors

Several commands, such as `nix-env -q` and `nix-env -i`, take a list of arguments that specify the packages on which to operate. These are extended regular expressions that must match the entire name of the package. (For details on regular expressions, see regex7.) 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. Here are some examples:

- `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`.

# Common options

This section lists the options that are common to all operations. These options are allowed for every subcommand, though they may not always have an effect.

- `--file` / `-f` path
  Specifies the Nix expression (designated below as the active Nix expression) used by the `--install`, `--upgrade`, and `--query --available` operations to obtain derivations. The default is `~/.nix-defexpr`.

  If the argument 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 include a single top-level directory containing at least a file named `default.nix`.

- `--profile` / `-p` path
  Specifies the profile to be used by those operations that operate on a profile (designated below as the active profile). A profile is a sequence of user environments called generations, one of which is the current generation.

- `--dry-run`
  For the `--install`, `--upgrade`, `--uninstall`, `--switch-generation`, `--delete-generations` and `--rollback` operations, this flag will cause `nix-env` to print what would be done if this flag had not been specified, without actually doing it.

  `--dry-run` also prints out which paths will be substituted (i.e., downloaded) and which paths will be built from source (because no substitute is available).

- `--system-filter` system
  By default, operations such as `--query --available` show derivations matching any platform. This option allows you to use derivations for the specified platform system.

# Files

- `~/.nix-defexpr`
  The source for the default Nix expressions used by the `--install`, `--upgrade`, and `--query --available` operations to obtain derivations. The `--file` option may be used to override this default.

  If `~/.nix-defexpr` is a file, it is loaded as a Nix expression. If the expression is a 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.

  If `~/.nix-defexpr` is a directory containing a `default.nix` file, that file is loaded as in the above paragraph.

  If `~/.nix-defexpr` 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 set, each expression under an attribute with the same name as the original file or subdirectory.

  For example, if `~/.nix-defexpr` contains two files, `foo.nix` and `bar.nix`, then the default Nix expression will essentially be

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

  The file `manifest.nix` is always ignored. 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.

  The command `nix-channel` places symlinks to the downloaded Nix expressions from each subscribed channel in this directory.

- `~/.nix-profile`
  A symbolic link to the user's current profile. By default, this symlink points to `prefix/var/nix/profiles/default`. The `PATH` environment variable should include `~/.nix-profile/bin` for the user environment to be visible to the user.

# Operation `--install`

## Synopsis

`nix-env` {`--install` | `-i`} args… [{`--prebuilt-only` | `-b`}] [{`--attr` | `-A`}] [`--from-expression`] [`-E`] [`--from-profile` path] [`--preserve-installed` | `-P`] [`--remove-all` | `-r`]

## Description

The install operation creates a new user environment, based on the current generation of the active profile, to which a set of store paths described by args is added. The arguments args map to store paths in a number of possible ways:

- By default, args is a set of derivation names denoting derivations in the active Nix expression. These are realised, and the resulting output paths are installed. Currently installed derivations with a name equal to the name of a derivation being added are removed unless the option `--preserve-installed` is specified.

  If there are multiple derivations matching a name in args that have the same name (e.g., `gcc-3.3.6` and `gcc-4.1.1`), then the derivation with the highest priority is used. A derivation can define a priority by declaring the `meta.priority` attribute. This attribute should be a number, with a higher value denoting a lower priority. The default priority is `0`.

  If there are multiple matching derivations with the same priority, then the derivation with the highest version will be installed.

  You can force the installation of multiple derivations with the same name by being specific about the versions. For instance, `nix-env -i gcc-3.3.6 gcc-4.1.1` will install both version of GCC (and will probably cause a user environment conflict!).

- If `--attr` (`-A`) is specified, the arguments are attribute paths that select attributes from the top-level Nix expression. This is faster than using derivation names and unambiguous. To find out the attribute paths of available packages, use `nix-env -qaP`.

- If `--from-profile` path is given, args is a set of names denoting installed store paths in the profile path. This is an easy way to copy user environment elements from one profile to another.

- If `--from-expression` is given, args are Nix functions that are called with the active Nix expression as their single argument. The derivations returned by those function calls are installed. This allows derivations to be specified in an unambiguous way, which is necessary if there are multiple derivations with the same name.

- If args are store derivations, then these are realised, and the resulting output paths are installed.

- If args are store paths that are not store derivations, then these are realised and installed.

- By default all outputs are installed for each derivation. That can be reduced by setting `meta.outputsToInstall`.

## Flags

- `--prebuilt-only` / `-b`
  Use only derivations for which a substitute is registered, i.e., there is a pre-built binary available that can be downloaded in lieu of building the derivation. Thus, no packages will be built from source.

- `--preserve-installed`; `-P`
  Do not remove derivations with a name matching one of the derivations being installed. Usually, trying to have two versions of the same package installed in the same generation of a profile will lead to an error in building the generation, due to file name clashes between the two versions. However, this is not the case for all packages.

- `--remove-all`; `-r`
  Remove all previously installed packages first. This is equivalent to running `nix-env -e '.*'` first, except that everything happens in a single transaction.

## Examples

To install a package using a specific attribute path from the active Nix expression:

    $ nix-env -iA gcc40mips
    installing `gcc-4.0.2'
    $ nix-env -iA xorg.xorgserver
    installing `xorg-server-1.2.0'

To install a specific version of `gcc` using the derivation name:

    $ nix-env --install gcc-3.3.2
    installing `gcc-3.3.2'
    uninstalling `gcc-3.1'

Using attribute path for selecting a package is preferred, as it is much faster and there will not be multiple matches.

Note the previously installed version is removed, since `--preserve-installed` was not specified.

To install an arbitrary version:

    $ nix-env --install gcc
    installing `gcc-3.3.2'

To install all derivations in the Nix expression `foo.nix`:

    $ nix-env -f ~/foo.nix -i '.*'

To copy the store path with symbolic name `gcc` from another profile:

    $ nix-env -i --from-profile /nix/var/nix/profiles/foo gcc

To install a specific store derivation (typically created by `nix-instantiate`):

    $ nix-env -i /nix/store/fibjb1bfbpm5mrsxc4mh2d8n37sxh91i-gcc-3.4.3.drv

To install a specific output path:

    $ nix-env -i /nix/store/y3cgx0xj1p4iv9x0pnnmdhr8iyg741vk-gcc-3.4.3

To install from a Nix expression specified on the command-line:

    $ nix-env -f ./foo.nix -i -E \
        'f: (f {system = "i686-linux";}).subversionWithJava'

I.e., this evaluates to `(f: (f {system = "i686-linux";}).subversionWithJava) (import ./foo.nix)`, thus selecting the `subversionWithJava` attribute from the set returned by calling the function defined in `./foo.nix`.

A dry-run tells you which paths will be downloaded or built from source:

    $ nix-env -f '<nixpkgs>' -iA hello --dry-run
    (dry run; not doing anything)
    installing ‘hello-2.10’
    this path will be fetched (0.04 MiB download, 0.19 MiB unpacked):
      /nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10
      ...

To install Firefox from the latest revision in the Nixpkgs/NixOS 14.12 channel:

    $ nix-env -f https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz -iA firefox

# Operation `--upgrade`

## Synopsis

`nix-env` {`--upgrade` | `-u`} args [`--lt` | `--leq` | `--eq` | `--always`] [{`--prebuilt-only` | `-b`}] [{`--attr` | `-A`}] [`--from-expression`] [`-E`] [`--from-profile` path] [`--preserve-installed` | `-P`]

## Description

The upgrade operation creates a new user environment, based on the current generation of the active profile, in which all store paths are replaced for which there are newer versions in the set of paths described by args. Paths for which there are no newer versions are left untouched; this is not an error. It is also not an error if an element of args matches no installed derivations.

For a description of how args is mapped to a set of store paths, see `--install`. If args describes multiple store paths with the same symbolic name, only the one with the highest version is installed.

## Flags

- `--lt`
  Only upgrade a derivation to newer versions. This is the default.

- `--leq`
  In addition to upgrading to newer versions, also “upgrade” to derivations that have the same version. Version are not a unique identification of a derivation, so there may be many derivations that have the same version. This flag may be useful to force “synchronisation” between the installed and available derivations.

- `--eq`
  Only “upgrade” to derivations that have the same version. This may not seem very useful, but it actually is, e.g., when there is a new release of Nixpkgs and you want to replace installed applications with the same versions built against newer dependencies (to reduce the number of dependencies floating around on your system).

- `--always`
  In addition to upgrading to newer versions, also “upgrade” to derivations that have the same or a lower version. I.e., derivations may actually be downgraded depending on what is available in the active Nix expression.

For the other flags, see `--install`.

## Examples

    $ nix-env --upgrade -A nixpkgs.gcc
    upgrading `gcc-3.3.1' to `gcc-3.4'

When there are no updates available, nothing will happen:

    $ nix-env --upgrade -A nixpkgs.pan

Using `-A` is preferred when possible, as it is faster and unambiguous but it is also possible to upgrade to a specific version by matching the derivation name:

    $ nix-env -u gcc-3.3.2 --always
    upgrading `gcc-3.4' to `gcc-3.3.2'

To try to upgrade everything (matching packages based on the part of the derivation name without version):

    $ nix-env -u
    upgrading `hello-2.1.2' to `hello-2.1.3'
    upgrading `mozilla-1.2' to `mozilla-1.4'

## Versions

The upgrade operation determines whether a derivation `y` is an upgrade of a derivation `x` by looking at their respective `name` attributes. The names (e.g., `gcc-3.3.1` are split into two parts: the package name (`gcc`), and the version (`3.3.1`). The version part starts after the first dash not followed by a letter. `x` is considered an upgrade of `y` if their package names match, and the version of `y` is higher than that of `x`.

The versions are compared by splitting them into contiguous components of numbers and letters. E.g., `3.3.1pre5` is split into `[3, 3, 1, "pre", 5]`. These lists are then compared lexicographically (from left to right). Corresponding components `a` and `b` are compared as follows. If they are both numbers, integer comparison is used. If `a` is an empty string and `b` is a number, `a` is considered less than `b`. The special string component `pre` (for pre-release) is considered to be less than other components. String components are considered less than number components. Otherwise, they are compared lexicographically (i.e., using case-sensitive string comparison).

This is illustrated by the following examples:

    1.0 < 2.3
    2.1 < 2.3
    2.3 = 2.3
    2.5 > 2.3
    3.1 > 2.3
    2.3.1 > 2.3
    2.3.1 > 2.3a
    2.3pre1 < 2.3
    2.3pre3 < 2.3pre12
    2.3a < 2.3c
    2.3pre1 < 2.3c
    2.3pre1 < 2.3q

# Operation `--uninstall`

## Synopsis

`nix-env` {`--uninstall` | `-e`} drvnames…

## Description

The uninstall operation creates a new user environment, based on the current generation of the active profile, from which the store paths designated by the symbolic names drvnames are removed.

## Examples

    $ nix-env --uninstall gcc
    $ nix-env -e '.*' (remove everything)

# Operation `--set`

## Synopsis

`nix-env` `--set` drvname

## Description

The `--set` operation modifies the current generation of a profile so that it contains exactly the specified derivation, and nothing else.

## Examples

The following updates a profile such that its current generation will contain just Firefox:

    $ nix-env -p /nix/var/nix/profiles/browser --set firefox

# Operation `--set-flag`

## Synopsis

`nix-env` `--set-flag` name value drvnames

## Description

The `--set-flag` operation allows meta attributes of installed packages to be modified. There are several attributes that can be usefully modified, because they affect the behaviour of `nix-env` or the user environment build script:

- `priority` can be changed to resolve filename clashes. The user environment build script uses the `meta.priority` attribute of derivations to resolve filename collisions between packages. Lower priority values denote a higher priority. For instance, the GCC wrapper package and the Binutils package in Nixpkgs both have a file `bin/ld`, so previously if you tried to install both you would get a collision. Now, on the other hand, the GCC wrapper declares a higher priority than Binutils, so the former’s `bin/ld` is symlinked in the user environment.

- `keep` can be set to `true` to prevent the package from being upgraded or replaced. This is useful if you want to hang on to an older version of a package.

- `active` can be set to `false` to “disable” the package. That is, no symlinks will be generated to the files of the package, but it remains part of the profile (so it won’t be garbage-collected). It can be set back to `true` to re-enable the package.

## Examples

To prevent the currently installed Firefox from being upgraded:

    $ nix-env --set-flag keep true firefox

After this, `nix-env -u` will ignore Firefox.

To disable the currently installed Firefox, then install a new Firefox while the old remains part of the profile:

    $ nix-env -q
    firefox-2.0.0.9 (the current one)

    $ nix-env --preserve-installed -i firefox-2.0.0.11
    installing `firefox-2.0.0.11'
    building path(s) `/nix/store/myy0y59q3ig70dgq37jqwg1j0rsapzsl-user-environment'
    collision between `/nix/store/...-firefox-2.0.0.11/bin/firefox'
      and `/nix/store/...-firefox-2.0.0.9/bin/firefox'.
    (i.e., can’t have two active at the same time)

    $ nix-env --set-flag active false firefox
    setting flag on `firefox-2.0.0.9'

    $ nix-env --preserve-installed -i firefox-2.0.0.11
    installing `firefox-2.0.0.11'

    $ nix-env -q
    firefox-2.0.0.11 (the enabled one)
    firefox-2.0.0.9 (the disabled one)

To make files from `binutils` take precedence over files from `gcc`:

    $ nix-env --set-flag priority 5 binutils
    $ nix-env --set-flag priority 10 gcc

# Operation `--query`

## Synopsis

`nix-env` {`--query` | `-q`} names… [`--installed` | `--available` | `-a`] [{`--status` | `-s`}] [{`--attr-path` | `-P`}] [`--no-name`] [{`--compare-versions` | `-c`}] [`--system`] [`--drv-path`] [`--out-path`] [`--description`] [`--meta`] [`--xml`] [`--json`] [{`--prebuilt-only` | `-b`}] [{`--attr` | `-A`} attribute-path]

## Description

The query operation displays information about either the store paths that are installed in the current generation of the active profile (`--installed`), or the derivations that are available for installation in the active Nix expression (`--available`). It only prints information about derivations whose symbolic name matches one of names.

The derivations are sorted by their `name` attributes.

## Source selection

The following flags specify the set of things on which the query operates.

- `--installed`
  The query operates on the store paths that are installed in the current generation of the active profile. This is the default.

- `--available`; `-a`
  The query operates on the derivations that are available in the active Nix expression.

## Queries

The following flags specify what information to display about the selected derivations. Multiple flags may be specified, in which case the information is shown in the order given here. Note that the name of the derivation is shown unless `--no-name` is specified.

- `--xml`
  Print the result in an XML representation suitable for automatic processing by other tools. The root element is called `items`, which contains a `item` element for each available or installed derivation. The fields discussed below are all stored in attributes of the `item` elements.

- `--json`
  Print the result in a JSON representation suitable for automatic processing by other tools.

- `--prebuilt-only` / `-b`
  Show only derivations for which a substitute is registered, i.e., there is a pre-built binary available that can be downloaded in lieu of building the derivation. Thus, this shows all packages that probably can be installed quickly.

- `--status`; `-s`
  Print the status of the derivation. The status consists of three characters. The first is `I` or `-`, indicating whether the derivation is currently installed in the current generation of the active profile. This is by definition the case for `--installed`, but not for `--available`. The second is `P` or `-`, indicating whether the derivation is present on the system. This indicates whether installation of an available derivation will require the derivation to be built. The third is `S` or `-`, indicating whether a substitute is available for the derivation.

- `--attr-path`; `-P`
  Print the attribute path of the derivation, which can be used to unambiguously select it using the `--attr` option available in commands that install derivations like `nix-env --install`. This option only works together with `--available`

- `--no-name`
  Suppress printing of the `name` attribute of each derivation.

- `--compare-versions` / `-c`
  Compare installed versions to available versions, or vice versa (if `--available` is given). This is useful for quickly seeing whether upgrades for installed packages are available in a Nix expression. A column is added with the following meaning:

  - `<` version
    A newer version of the package is available or installed.

  - `=` version
    At most the same version of the package is available or installed.

  - `>` version
    Only older versions of the package are available or installed.

  - `- ?`
    No version of the package is available or installed.

- `--system`
  Print the `system` attribute of the derivation.

- `--drv-path`
  Print the path of the store derivation.

- `--out-path`
  Print the output path of the derivation.

- `--description`
  Print a short (one-line) description of the derivation, if available. The description is taken from the `meta.description` attribute of the derivation.

- `--meta`
  Print all of the meta-attributes of the derivation. This option is only available with `--xml` or `--json`.

## Examples

To show installed packages:

    $ nix-env -q
    bison-1.875c
    docbook-xml-4.2
    firefox-1.0.4
    MPlayer-1.0pre7
    ORBit2-2.8.3
    …

To show available packages:

    $ nix-env -qa
    firefox-1.0.7
    GConf-2.4.0.1
    MPlayer-1.0pre7
    ORBit2-2.8.3
    …

To show the status of available packages:

    $ nix-env -qas
    -P- firefox-1.0.7   (not installed but present)
    --S GConf-2.4.0.1   (not present, but there is a substitute for fast installation)
    --S MPlayer-1.0pre3 (i.e., this is not the installed MPlayer, even though the version is the same!)
    IP- ORBit2-2.8.3    (installed and by definition present)
    …

To show available packages in the Nix expression `foo.nix`:

    $ nix-env -f ./foo.nix -qa
    foo-1.2.3

To compare installed versions to what’s available:

    $ nix-env -qc
    ...
    acrobat-reader-7.0 - ?      (package is not available at all)
    autoconf-2.59      = 2.59   (same version)
    firefox-1.0.4      < 1.0.7  (a more recent version is available)
    ...

To show all packages with “`zip`” in the name:

    $ nix-env -qa '.*zip.*'
    bzip2-1.0.6
    gzip-1.6
    zip-3.0
    …

To show all packages with “`firefox`” or “`chromium`” in the name:

    $ nix-env -qa '.*(firefox|chromium).*'
    chromium-37.0.2062.94
    chromium-beta-38.0.2125.24
    firefox-32.0.3
    firefox-with-plugins-13.0.1
    …

To show all packages in the latest revision of the Nixpkgs repository:

    $ nix-env -f https://github.com/NixOS/nixpkgs/archive/master.tar.gz -qa

# Operation `--switch-profile`

## Synopsis

`nix-env` {`--switch-profile` | `-S`} path

## Description

This operation makes path the current profile for the user. That is, the symlink `~/.nix-profile` is made to point to path.

## Examples

    $ nix-env -S ~/my-profile

# Operation `--list-generations`

## Synopsis

`nix-env` `--list-generations`

## Description

This operation print a list of all the currently existing generations for the active profile. These may be switched to using the `--switch-generation` operation. It also prints the creation date of the generation, and indicates the current generation.

## Examples

    $ nix-env --list-generations
      95   2004-02-06 11:48:24
      96   2004-02-06 11:49:01
      97   2004-02-06 16:22:45
      98   2004-02-06 16:24:33   (current)

# Operation `--delete-generations`

## Synopsis

`nix-env` `--delete-generations` generations

## Description

This operation deletes the specified generations of the current profile. The generations can be a list of generation numbers, the special value `old` to delete all non-current generations, a value such as `30d` to delete all generations older than the specified number of days (except for the generation that was active at that point in time), or a value such as `+5` to keep the last `5` generations ignoring any newer than current, e.g., if `30` is the current generation `+5` will delete generation `25` and all older generations. Periodically deleting old generations is important to make garbage collection effective.

## Examples

    $ nix-env --delete-generations 3 4 8

    $ nix-env --delete-generations +5

    $ nix-env --delete-generations 30d

    $ nix-env -p other_profile --delete-generations old

# Operation `--switch-generation`

## Synopsis

`nix-env` {`--switch-generation` | `-G`} generation

## Description

This operation makes generation number generation the current generation of the active profile. That is, if the `profile` is the path to the active profile, then the symlink `profile` is made to point to `profile-generation-link`, which is in turn a symlink to the actual user environment in the Nix store.

Switching will fail if the specified generation does not exist.

## Examples

    $ nix-env -G 42
    switching from generation 50 to 42

# Operation `--rollback`

## Synopsis

`nix-env` `--rollback`

## Description

This operation switches to the “previous” generation of the active profile, that is, the highest numbered generation lower than the current generation, if it exists. It is just a convenience wrapper around `--list-generations` and `--switch-generation`.

## Examples

    $ nix-env --rollback
    switching from generation 92 to 91

    $ nix-env --rollback
    error: no generation older than the current (91) exists

# Environment variables

- `NIX_PROFILE`
  Location of the Nix profile. Defaults to the target of the symlink `~/.nix-profile`, if it exists, or `/nix/var/nix/profiles/default` otherwise.