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83 lines
2.5 KiB
Markdown
83 lines
2.5 KiB
Markdown
# Name
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`nix-env --set-flag` - modify meta attributes of installed packages
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# Synopsis
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`nix-env` `--set-flag` *name* *value* *drvnames*
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# Description
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The `--set-flag` operation allows meta attributes of installed packages
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to be modified. There are several attributes that can be usefully
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modified, because they affect the behaviour of `nix-env` or the user
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environment build script:
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- `priority` can be changed to resolve filename clashes. The user
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environment build script uses the `meta.priority` attribute of
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derivations to resolve filename collisions between packages. Lower
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priority values denote a higher priority. For instance, the GCC
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wrapper package and the Binutils package in Nixpkgs both have a file
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`bin/ld`, so previously if you tried to install both you would get a
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collision. Now, on the other hand, the GCC wrapper declares a higher
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priority than Binutils, so the former’s `bin/ld` is symlinked in the
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user environment.
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- `keep` can be set to `true` to prevent the package from being
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upgraded or replaced. This is useful if you want to hang on to an
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older version of a package.
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- `active` can be set to `false` to “disable” the package. That is, no
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symlinks will be generated to the files of the package, but it
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remains part of the profile (so it won’t be garbage-collected). It
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can be set back to `true` to re-enable the package.
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{{#include ./opt-common.md}}
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{{#include ../opt-common.md}}
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{{#include ../env-common.md}}
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# Examples
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To prevent the currently installed Firefox from being upgraded:
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```console
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$ nix-env --set-flag keep true firefox
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```
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After this, `nix-env --upgrade ` will ignore Firefox.
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To disable the currently installed Firefox, then install a new Firefox
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while the old remains part of the profile:
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```console
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$ nix-env --query
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firefox-2.0.0.9 (the current one)
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$ nix-env --preserve-installed --install firefox-2.0.0.11
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installing `firefox-2.0.0.11'
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building path(s) `/nix/store/myy0y59q3ig70dgq37jqwg1j0rsapzsl-user-environment'
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collision between `/nix/store/...-firefox-2.0.0.11/bin/firefox'
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and `/nix/store/...-firefox-2.0.0.9/bin/firefox'.
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(i.e., can’t have two active at the same time)
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$ nix-env --set-flag active false firefox
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setting flag on `firefox-2.0.0.9'
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$ nix-env --preserve-installed --install firefox-2.0.0.11
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installing `firefox-2.0.0.11'
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$ nix-env --query
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firefox-2.0.0.11 (the enabled one)
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firefox-2.0.0.9 (the disabled one)
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```
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To make files from `binutils` take precedence over files from `gcc`:
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```console
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$ nix-env --set-flag priority 5 binutils
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$ nix-env --set-flag priority 10 gcc
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```
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