Provided by: nix-bin_2.16.1+dfsg-3ubuntu1_amd64 bug

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.

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

       Most Nix commands accept the following command-line options:

       • --help
         Prints out a summary of the command syntax and exits.

       • --version
         Prints out the Nix version number on standard output and exits.

       • --verbose / -v
         Increases  the  level of verbosity of diagnostic messages printed on standard error. For
         each Nix operation, the information printed on  standard  output  is  well-defined;  any
         diagnostic information is printed on standard error, never on standard output.

         This  option  may  be  specified  repeatedly.  Currently, the following verbosity levels
         exist:

         • 0
           “Errors only”: only print messages explaining why the Nix invocation failed.

         • 1
           “Informational”: print useful messages about what Nix is doing. This is the default.

         • 2
           “Talkative”: print more informational messages.

         • 3
           “Chatty”: print even more informational messages.

         • 4
           “Debug”: print debug information.

         • 5
           “Vomit”: print vast amounts of debug information.

       • --quiet
         Decreases the level of verbosity of diagnostic messages printed on standard error.  This
         is the inverse option to -v / --verbose.

         This option may be specified repeatedly. See the previous verbosity levels list.

       • --log-format format
         This  option  can  be used to change the output of the log format, with format being one
         of:

         • raw
           This is the raw format, as outputted by nix-build.

         • internal-json
           Outputs the logs in a structured manner.

                  Warning

                  While the schema itself is relatively stable, the format of the  error-messages
                  (namely of the msg-field) can change between releases.

         • bar
           Only display a progress bar during the builds.

         • bar-with-logs
           Display the raw logs, with the progress bar at the bottom.

       • --no-build-output / -Q
         By  default,  output written by builders to standard output and standard error is echoed
         to the Nix command’s standard error. This option suppresses this  behaviour.  Note  that
         the  builder’s  standard  output  and  error  are  always  written  to  a  log  file  in
         prefix/nix/var/log/nix.

       • --max-jobs / -j number
         Sets the maximum number of build jobs that Nix will perform in parallel to the specified
         number.  Specify  auto to use the number of CPUs in the system. The default is specified
         by the max-jobs configuration setting, which itself defaults to 1.  A  higher  value  is
         useful on SMP systems or to exploit I/O latency.

         Setting  it  to 0 disallows building on the local machine, which is useful when you want
         builds to happen only on remote builders.

       • --cores
         Sets the value  of  the  NIX_BUILD_CORES  environment  variable  in  the  invocation  of
         builders.  Builders  can  use  this  variable at their discretion to control the maximum
         amount  of  parallelism.  For  instance,  in  Nixpkgs,  if  the   derivation   attribute
         enableParallelBuilding  is  set to true, the builder passes the -jN flag to GNU Make. It
         defaults to the value of the cores configuration setting, if set, or  1  otherwise.  The
         value 0 means that the builder should use all available CPU cores in the system.

       • --max-silent-time
         Sets  the  maximum number of seconds that a builder can go without producing any data on
         standard output or standard error. The  default  is  specified  by  the  max-silent-time
         configuration setting. 0 means no time-out.

       • --timeout
         Sets  the  maximum number of seconds that a builder can run. The default is specified by
         the timeout configuration setting. 0 means no timeout.

       • --keep-going / -k
         Keep going in case of failed builds, to  the  greatest  extent  possible.  That  is,  if
         building  an  input of some derivation fails, Nix will still build the other inputs, but
         not the derivation itself. Without this option, Nix stops if any build fails (except for
         builds  of  substitutes),  possibly  killing  builds in progress (in case of parallel or
         distributed builds).

       • --keep-failed / -K
         Specifies that in case of a build failure, the temporary directory (usually in /tmp)  in
         which  the  build  takes place should not be deleted. The path of the build directory is
         printed as an informational message.

       • --fallback
         Whenever Nix attempts to build a derivation for which substitutes  are  known  for  each
         output  path, but realising the output paths through the substitutes fails, fall back on
         building the derivation.

         The most common scenario in which this is useful is when we have registered  substitutes
         in  order  to  perform  binary  distribution  from,  say,  a  network repository. If the
         repository is down, the realisation of the derivation will fail.  When  this  option  is
         specified, Nix will build the derivation instead. Thus, installation from binaries falls
         back on installation from source. This option is not the default since it  is  generally
         not  desirable  for  a  transient failure in obtaining the substitutes to lead to a full
         build from source (with the related consumption of resources).

       • --readonly-mode
         When this option is used, no attempt  is  made  to  open  the  Nix  database.  Most  Nix
         operations do need database access, so those operations will fail.

       • --arg name value
         This  option  is  accepted  by  nix-env,  nix-instantiate, nix-shell and nix-build. When
         evaluating Nix expressions, the expression evaluator  will  automatically  try  to  call
         functions  that  it  encounters.  It  can  automatically  call functions for which every
         argument has a default value (e.g., { argName ?  defaultValue }: ...). With  --arg,  you
         can  also  call  functions  that  have  arguments without a default value (or override a
         default value). That is, if the evaluator encounters a function with an  argument  named
         name, it will call it with value value.

         For instance, the top-level default.nix in Nixpkgs is actually a function:

       { # The system (e.g., `i686-linux') for which to build the packages.
         system ? builtins.currentSystem
         ...
       }: ...

              So  if  you  call  this  Nix expression (e.g., when you do nix-env --install --attr
              pkgname),  the  function   will   be   called   automatically   using   the   value
              builtins.currentSystem  for the system argument. You can override this using --arg,
              e.g., nix-env --install --attr pkgname --arg system  \"i686-freebsd\".  (Note  that
              since the argument is a Nix string literal, you have to escape the quotes.)

       • --argstr name value
         This  option  is  like  --arg,  only  the value is not a Nix expression but a string. So
         instead of --arg system \"i686-linux\" (the outer quotes are to keep  the  shell  happy)
         you can say --argstr system i686-linux.

       • --attr / -A attrPath
         Select  an  attribute  from the top-level Nix expression being evaluated. (nix-env, nix-
         instantiate, nix-build and nix-shell only.) The attribute path attrPath is a sequence of
         attribute names separated by dots. For instance, given a top-level Nix expression e, the
         attribute path xorg.xorgserver would cause the expression e.xorg.xorgserver to be  used.
         See nix-env --install for some concrete examples.

         In  addition  to attribute names, you can also specify array indices.  For instance, the
         attribute path foo.3.bar selects the bar attribute of the fourth element of the array in
         the foo attribute of the top-level expression.

       • --expr / -E
         Interpret  the  command  line  arguments  as  a list of Nix expressions to be parsed and
         evaluated, rather than as a list of file names  of  Nix  expressions.  (nix-instantiate,
         nix-build and nix-shell only.)

         For  nix-shell,  this option is commonly used to give you a shell in which you can build
         the packages returned by the expression. If you want to get a shell  which  contain  the
         built  packages  ready  for  use,  give  your  expression  to  the  nix-shell --packages
         convenience flag instead.

       • -I path
         Add an entry to the Nix expression search path.   This  option  may  be  given  multiple
         times.  Paths added through -I take precedence over NIX_PATH.

       • --option name value
         Set  the  Nix  configuration  option  name  to value. This overrides settings in the Nix
         configuration file (see nix.conf5).

       • --repair
         Fix corrupted or missing store paths by redownloading or rebuilding them. Note that this
         is slow because it requires computing a cryptographic hash of the contents of every path
         in the closure of the build. Also note the warning under nix-store --repair-path.

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

       Most Nix commands interpret the following environment variables:

       • IN_NIX_SHELL
         Indicator that tells if the current environment was set up by nix-shell. It can have the
         values pure or impure.

       • NIX_PATH
         A colon-separated list of directories used to look up the location  of  Nix  expressions
         using  paths enclosed in angle brackets (i.e., <path>), e.g. /home/eelco/Dev:/etc/nixos.
         It can be extended using the -I option.

         If NIX_PATH is not set at all, Nix will fall back to the following list  in  impure  and
         unrestricted evaluation mode:

         1.     $HOME/.nix-defexpr/channels
         2.     nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixpkgs
         3.     /nix/var/nix/profiles/per-user/root/channels

         If  NIX_PATH  is  set  to an empty string, resolving search paths will always fail.  For
         example, attempting to use <nixpkgs> will produce:

       error: file 'nixpkgs' was not found in the Nix search path

       • NIX_IGNORE_SYMLINK_STORE
         Normally, the Nix store directory (typically /nix/store) is not allowed to  contain  any
         symlink   components.   This   is   to   prevent  “impure”  builds.  Builders  sometimes
         “canonicalise” paths by resolving all symlink  components.  Thus,  builds  on  different
         machines  (with  /nix/store  resolving  to  different  locations)  could yield different
         results. This is generally not a problem, except when builds are  deployed  to  machines
         where /nix/store resolves differently. If you are sure that you’re not going to do that,
         you can set NIX_IGNORE_SYMLINK_STORE to 1.

         Note that if you’re symlinking the Nix store so that you can  put  it  on  another  file
         system  than  the  root file system, on Linux you’re better off using bind mount points,
         e.g.,

       $ mkdir /nix
       $ mount -o bind /mnt/otherdisk/nix /nix

              Consult the mount 8 manual page for details.

       • NIX_STORE_DIR
         Overrides the location of the Nix store (default prefix/store).

       • NIX_DATA_DIR
         Overrides the location of the Nix static data directory (default prefix/share).

       • NIX_LOG_DIR
         Overrides the location of the Nix log directory (default prefix/var/log/nix).

       • NIX_STATE_DIR
         Overrides the location of the Nix state directory (default prefix/var/nix).

       • NIX_CONF_DIR
         Overrides  the  location  of   the   system   Nix   configuration   directory   (default
         prefix/etc/nix).

       • NIX_CONFIG
         Applies settings from Nix configuration from the environment.  The content is treated as
         if it was read from a Nix configuration file.  Settings are  separated  by  the  newline
         character.

       • NIX_USER_CONF_FILES
         Overrides the location of the Nix user configuration files to load from.

         The  default  are  the locations according to the XDG Base Directory Specification.  See
         the XDG Base Directories sub-section for details.

         The variable is treated as a list separated by the : token.

       • TMPDIR
         Use the specified directory to store  temporary  files.  In  particular,  this  includes
         temporary  build  directories;  these can take up substantial amounts of disk space. The
         default is /tmp.

       • NIX_REMOTE
         This variable should be set to daemon if you want to use the Nix daemon to  execute  Nix
         operations.  This is necessary in multi-user Nix installations. If the Nix daemon’s Unix
         socket  is   at   some   non-standard   path,   this   variable   should   be   set   to
         unix://path/to/socket. Otherwise, it should be left unset.

       • NIX_SHOW_STATS
         If  set  to  1,  Nix will print some evaluation statistics, such as the number of values
         allocated.

       • NIX_COUNT_CALLS
         If set to 1, Nix will print how  often  functions  were  called  during  Nix  expression
         evaluation. This is useful for profiling your Nix expressions.

       • GC_INITIAL_HEAP_SIZE
         If  Nix  has  been configured to use the Boehm garbage collector, this variable sets the
         initial size of the heap in bytes. It defaults to 384 MiB. Setting it  to  a  low  value
         reduces  memory  consumption,  but  will increase runtime due to the overhead of garbage
         collection.

   XDG Base Directories
       Nix follows the XDG Base Directory Specification.

       For backwards compatibility, Nix commands will follow the standard only when use-xdg-base-
       directories  is  enabled.   New  Nix  commands  (experimental)  conform to the standard by
       default.

       The following environment variables are used to determine locations of various  state  and
       configuration files:

       • [XDG_CONFIG_HOME]{#env-XDGCONFIGHOME} (default ~/.config)
       • [XDG_STATE_HOME]{#env-XDGSTATEHOME} (default ~/.local/state)
       • [XDG_CACHE_HOME]{#env-XDGCACHEHOME} (default ~/.cache)

Examples

       $ nix-env --switch-profile ~/my-profile

                                                                       nix-env –switch-profile(1)