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    Nix-Event

    nix-env

    nix-env documentation stable version
    nix-env documentation unstable version

    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

    Selectors

    Several commands, such as nix-env --query and nix-env --install , 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 regex(7).) 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.

    Files

    nix-env operates on the following files.

    Default Nix expression

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

    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.

    For 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 user's current channels profile in this directory. This makes all subscribed channels available as attributes in the default expression.

    A symlink that ensures that nix-env can find your 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.nix-env: ../nix-env.md

    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.

    Options

    The following options are allowed for all nix-env operations, but 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.

    Common Options

    ![[NixOS Commun store cmd#[Common Options](https //nixos.org/manual/nix/unstable/command-ref/nix-store/add-fixed common-options)]]

    XDG Base Directories

    ![[NixOS Commun store cmd#[XDG Base Directories](https //nixos.org/manual/nix/unstable/command-ref/nix-store/add xdg-base-directories)]]

    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.

    Common Environment Variables

    ![[NixOS Commun store cmd#[Common Environment Variables](https //nixos.org/manual/nix/unstable/command-ref/nix-store/add-fixed common-environment-variables)]]

    nix-env --delete-generations

    nix-env --delete-generations documentation stable version
    nix-env -- delete-generations documentation unstable version

    Name

    nix-env --delete-generations - delete profile generations

    Synopsis

    nix-env --delete-generations _generations_

    Description

    This operation deletes the specified generations of the current profile.

    generations can be a one of the following:

    • <number>...:
      A list of generation numbers, each one a separate command-line argument.

      Delete exactly the profile generations given by their generation number. Deleting the current generation is not allowed.

    • The special value old

      Delete all generations except the current one.

      WARNING

      Older and newer generations will be deleted by this operation.

      One might expect this to just delete older generations than the curent one, but that is only true if the current generation is also the latest. Because one can roll back to a previous generation, it is possible to have generations newer than the current one. They will also be deleted.

    • <number>d:
      The last number days

      Example: 30d

      Delete all generations created more than number days ago, except the most recent one of them. This allows rolling back to generations that were available within the specified period.

    • +<number>:
      The last number generations up to the present

      Example: +5

      Keep the last number generations, along with any newer than current.

    Periodically deleting old generations is important to make garbage collection effective. The is because profiles are also garbage collection roots — any store object reachable from a profile is "alive" and ineligible for deletion.

    Examples

    Delete explicit generation numbers

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

    Delete the generations numbered 3, 4, and 8, so long as the current active generation is not any of those.

    Keep most-recent by count (number of generations)

    $ nix-env --delete-generations +5

    Suppose 30 is the current generation, and we currently have generations numbered 20 through 32.

    Then this command will delete generations 20 through 25 (<= 30 - 5), and keep generations 26 through 31 (> 30 - 5).

    Keep most-recent by time (number of days)

    $ nix-env --delete-generations 30d

    This command will delete all generations older than 30 days, except for the generation that was active 30 days ago (if it currently exists).

    Delete all older

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

    nix-env --install

    nix-env --install documentation stable version
    nix-env --install documentation unstable version

    Name

    nix-env --install - add packages to user environment

    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. It is 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 default 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 5.

      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 --install 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 default Nix expression. This is faster than using derivation names and unambiguous. Show the attribute paths of available packages with nix-env --query:

       nix-env --query --available --attr-path

    • 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 language functions that are called with the default 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. This can be overridden by adding a meta.outputsToInstall attribute on the derivation listing a subset of the output names.

      Example:

      The file example.nix defines a derivation with two outputs foo and bar, each containing a file.

      # example.nix 

let   
    pkgs = import <nixpkgs> {};   
    command = ''     
	    ${pkgs.coreutils}/bin/mkdir -p $foo $bar     
	    echo foo > $foo/foo-file     
	    echo bar > $bar/bar-file   
    ''; 
in 
	derivation {   
		name = "example";   
		builder = "${pkgs.bash}/bin/bash";   
		args = [ "-c" command ];   
		outputs = [ "foo" "bar" ];   
		system = builtins.currentSystem; 
	}

      Installing from this Nix expression will make files from both outputs appear in the current profile.

      $ nix-env --install --file example.nix 
installing 'example' 
$ ls ~/.nix-profile 
foo-file 
bar-file 
manifest.nix

      Adding meta.outputsToInstall to that derivation will make nix-env only install files from the specified outputs.

      # example-outputs.nix 
import ./example.nix // { meta.outputsToInstall = [ "bar" ]; }

      $ nix-env --install --file example-outputs.nix 
installing 'example' 
$ ls ~/.nix-profile 
bar-file 
manifest.nix

    Options

    • --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 --uninstall '.*' 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 --install --attr gcc40mips 
installing `gcc-4.0.2' 
$ nix-env --install --attr 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 --file ~/foo.nix --install '.*'

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

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

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

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

    To install a specific output path:

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

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

    $ nix-env --file ./foo.nix --install --expr \     
	'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 --file '<nixpkgs>' --install --attr 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 --file https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz --install --attr firefox

    nix-env --list-generations

    nix-env --list-generations documentation stable version
    nix-env --list-generations documentation unstable version

    Name

    nix-env --list-generations - list profile 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)

    nix-env --query

    nix-env --query documentation stable version
    nix-env --query documentation unstable version

    Name

    nix-env --query - display information about packages

    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 --query 
bison-1.875c 
docbook-xml-4.2 
firefox-1.0.4 
MPlayer-1.0pre7 
ORBit2-2.8.3 
…

    To show available packages:

    $ nix-env --query --available 
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 --query --available --status 
-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 --file ./foo.nix --query --available 
foo-1.2.3

    To compare installed versions to what’s available:

    $ nix-env --query --compare-versions 
... 
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 --query --available '.*zip.*' 
bzip2-1.0.6 
gzip-1.6 
zip-3.0 
…

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

    $ nix-env --query --available '.*(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 --file https://github.com/NixOS/nixpkgs/archive/master.tar.gz --query --available

    nix-event --rollback

    nix-env --rollback documentation stable version
    nix-env --rollback documentation unstable version

    Name

    nix-env --rollback - set user environment to previous generation

    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

    nix-event --set-flag

    nix-env --set-flag documentation stable version
    nix-env --set-flag documentation unstable version

    Name

    nix-env --set-flag - modify meta attributes of installed packages

    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 --upgrade will ignore Firefox.

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

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

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

$ nix-env --query 
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

    nix-event --set

    nix-env --set documentation stable version
    nix-env --set documentation unstable version

    Name

    nix-env --set - set profile to contain a specified derivation

    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 --profile /nix/var/nix/profiles/browser --set firefox

    nix-env --switch-generation

    nix-env --switch-generation documentation stable version
    nix-env --switch-generation documentation unstable version

    Name

    nix-env --switch-generation - set user environment to given profile 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 --switch-generation 
42 switching from generation 50 to 42

    nix-env --switch-profile

    nix-env --switch-profile documentation stable version
    nix-env --switch-profile documentation unstable version

    Name

    nix-env --switch-profile - set user environment to given 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 --switch-profile ~/my-profile

    nix-env --uninstall

    nix-env --uninstall documentation stable version
    nix-env --uninstall documentation unstable version

    Name

    nix-env --uninstall - remove packages from user environment

    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 --uninstall '.*' (remove everything)

    nix-env --upgrade

    nix-env --upgrade documentation stable version
    nix-env --upgrade documentation unstable version

    Name

    nix-env --upgrade - upgrade packages in user environment

    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.

    • --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.

    Examples

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

    When there are no updates available, nothing will happen:

    $ nix-env --upgrade --attr 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 --upgrade 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 --upgrade 
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. y is considered an upgrade of x 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
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