USE flag

USE flags are a core feature of Gentoo, and a good understanding of how to deal with them is needed for administering your Gentoo system.

Declaring USE flags
Setting USE flags can be done in and/or. For details see Handbook:Parts/Working/USE#Using USE flags.

USEful comands
To check if a certain USE flag is activated and which packages use it, run:

Replace  with the USE flag to be checked.

emerge command options
The emerge command has some USE flag related options like For details see man 1 emerge
 * emerge --changed-use (-U)
 * emerge --complete-graph-if-new-use < y | n >
 * emerge --newuse (-N)

Tools
Some tools are available for analyzing and managing USE flags:
 * euse
 * quse - for details see man 1 quse
 * equery hasuse (USE flag)
 * equery uses (package name)
 * ufed
 * - GTK Utility to help manage Portage's user config files
 * eix eix --use (USE flag), eix --installed-with-use (USE flag), eix --installed-without-use (USE flag)
 * - GTK Utility to help manage Portage's user config files
 * eix eix --use (USE flag), eix --installed-with-use (USE flag), eix --installed-without-use (USE flag)

External resources

 * https://www.gentoo.org/support/use-flags/ - The full USE flag index.
 * https://devmanual.gentoo.org/general-concepts/use-flags/