A proposal was raised a month ago for Fedora Linux 44 to replace the kernel’s frame-buffer console “FBCON” with KMSCON in user-space. The Fedora Engineering and Steering Committee (FESCo) has now granted approval for making this change in Fedora 44 as part of a larger foal to eventually deprecate FBCON/FBDEV emulation in the kernel.
There is some apprehension if all the proper fall-backs will be in place and robust enough in the event of any problems with this user-space console solution, but ultimately there was unanimous approval in the FESCo ticket for going ahead with these KMSCON plans for Fedora 44.
Fedora’s change proposal explains:
“fbcon is a terminal emulator in the kernel, which is not well maintained (it lost scrolling support a few years ago due to a CVE), and requires a fbdev emulation layer in the kernel, as all GPU drivers are using the newer drm interface. It still requires userspace executable like getty and bash to be useful.
kmscon is a simple terminal emulator based on linux kernel mode setting (KMS). It can replace fbcon for VT console, and provide better keyboard support, and better security.
This change will do the following: Install kmscon by default, and update the symbolic link /usr/lib/systemd/system/[email protected] to point to [email protected], to start kmscon by default when switching VT. kmscon should be the default also on non-graphical installation, as it doesn’t require any graphic library (only libdrm, to access the framebuffer).
This change won’t affect the installation, the boot process (like encryption password fallback), as fbcon will still be compiled in the kernel. User can still revert to fbcon if they want, or if kmscon has issue on their setup. If kmscon fails to launch, it will fallback to getty/fbcon.
Currently kmscon depends on opengl/mesa, because it has an optional opengl backend. But we don’t want that on non-graphical server installation. I will split the package in two, having something like kmscon and kmscon-gl for the optional gl renderer.”
This is a great chance for KMSCON to show off its ability and gain greater exposure for ultimately getting picked up by other Linux distributions too. Plus part of the long-term goal for many Linux developers to eventually see FBCON/FBDEV emulation deprecated in the Linux kernel.
Those unfamiliar with KMSCON or wanting to check out this user-space console can find it via GitHub. New releases continue to be frequent in ironing out shortcomings and providing additional functionality for modern Linux systems.
