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.

       {{#include ./opt-common.md}}

       {{#include ../opt-common.md}}

       {{#include ../env-common.md}}

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-env --set-flag(1)