User:Sam/Portage help/Understanding REQUIRED USE

Example 1
Here's a typical example of a REQUIRED_USE error/conflict:

Let's break this down a bit. The key part is: The following REQUIRED_USE flag constraints are unsatisfied: wayland? ( gles2 )

i.e. "If the wayland USE flag is enabled for media-libs/libsdl2, you must enable the gles2 flag for it as well."

Example 2
Here's another example:

Let's break this down a bit. The key part is: The following REQUIRED_USE flag constraints are unsatisfied: device-mapper-only? ( !lvm2create-initrd !sanlock !thin ) static-libs? ( static !udev )

There's two parts to this:


 * 1) If the device-mapper-only USE flag is enabled for sys-fs/lvm2, you must turn off the lvm2create-initrd, sanlock, thin flags
 * 2) If the static-libs USE flag is enabled, you must have the static flag on and the udev flag off.