Rootless

Revision 1 as of 2009-11-03 02:22:32

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Summary

For video drivers that support kernel mode-setting (KMS), X can be set up to run as a non-root user.

Background

Historically, X has been responsible for setting up the graphics modes (resolutions, refresh rates, etc.) X did this by talking to the hardware directly, which it could only do if it ran with root privileges. The reason X was tasked with doing this work was to keep graphics as platform-agnostic as possible, so the same graphics code could be used for BSD and other *nix flavors.

Today, the feeling is that this mode-setting logic should be moved into the kernel. Some video drivers, such as the -intel driver, now have this 'kernel mode-setting' (KMS) ability implemented. In karmic, -intel already uses KMS by default, and the -ati driver will run with KMS if the kernel is booted with the 'radeon.modeset=1' parameter, but it is not set as the default due to stability concerns. But other drivers in Karmic, such as -fglrx and -nvidia, do not support KMS at all.

References