What USE flags exist
There are two types of USE flags: global and local USE flags.
- A global USE flag is used by several packages, system-wide. This is what most people see as USE flags. A list of available global USE flags can be found on the main site or locally in the /usr/portage/profiles/use.desc file.
- A local USE flag is used by a single package to make package-specific decisions. A list of available local USE flags can be found on the main site or locally in the /usr/portage/profiles/use.local.desc file.
To make it easy for users to search and pick USE flags, we already provide a default USE setting. This setting is a collection of USE flags we think are commonly used by the Gentoo users. This default setting is declared in the make.defaults files that are part of the selected profile.
The profile the system listens to is pointed to by the /etc/portage/make.profile symlink. Each profile works on top of other profiles, and the end result is therefore the sum of all profiles. The top profile is the base profile (/usr/portage/profiles/base).
To view the currently active USE flags (completely), use emerge --info:
emerge --info | grep ^USE
emerge -1v app-portage/cpuid2cpuflags # may be app-portage/cpuinfo2cpuflags cpuinfo2cpuflags-x86
livecd ~ # cpuinfo2cpuflags-x86 CPU_FLAGS_X86: aes avx avx2 fma3 mmx mmxext popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3
INPUT_DEVICES="evdev" VIDEO_CARDS="intel nvidia"