# KMSCON

Related articles

- KMS
- systemd

From the project GitHub page:

  Kmscon is a simple terminal emulator based on linux kernel mode setting (KMS). It is an attempt to replace the in-kernel VT implementation with a userspace console.

## Features

Kmscon can function as a drop-in replacement for the in-kernel linux-console. Features include:

- Full vt220 to vt510 implementation.
- Full internationalization support:
  - Kmscon supports printing full Unicode glyphs, including the CJK ones.
  - Kmscon provides internationalized keyboard handling through libxkbcommon, thus allowing it to use the full range of keyboard layouts supported in X keyboard.
- Hardware accelerated rendering.
- Multi-seat capability.

Note: In order to be able to log into a kmscon console as root, you have to disable the `pam_securetty` module by removing or commenting out the corresponding line in `/etc/pam.d/login`.

## Install

Despite its name, KMS is not a hard requirement for kmscon. Kmscon supports the following video backends: fbdev (Linux fbdev video backend), drm2d (Linux DRM software-rendering backend), drm3d (Linux DRM hardware-rendering backend). Make sure one of them is available on your system.

Install kmscon from one of the official repositories. Alternatively, you can install kmscon-git from the AUR.

To enable it for the TTY1 run:

    # rm /etc/systemd/system/getty.target.wants/getty@tty1.service
    # systemctl enable kmsconvt@tty1.service

## Replacing Getty (agetty)

As root, issue:

    # ln -s /usr/lib/systemd/system/kmsconvt\@.service /etc/systemd/system/autovt\@.service

This will make systemd start KMSCON instead of agetty on each VT. Or more precisely, this will make systemd-logind use kmsconvt@.service instead of getty@.service for new VTs. In fact, all other units/scripts/... that use getty@.service will not be affected by this change.

If KMSCON cannot start for whatever reason, this unit will cause getty@.service to be started instead. So you will always have a safe fallback. Furthermore, if no VTs are available, this unit will not start anything.

## CJK support

Kmscon supports rendering CJK characters through the default font engine pango. However, fontconfig has to be globally configured to map the monospace font alias to proper CJK fonts. For Chinese users, the following template is provided and proved to result in satisfactory Chinese characters rendering:

    /etc/fonts/conf.d/99-kmscon.conf

    <?xml version="1.0"?>
    <!DOCTYPE fontconfig SYSTEM "fonts.dtd">
    <fontconfig>
    <match>
            <test name="family"><string>monospace</string></test>
            <edit name="family" mode="prepend" binding="strong">
                    <string>DejaVu Sans Mono</string>
                    <string>WenQuanYi Micro Hei Mono</string>
            </edit>
    </match>
    </fontconfig>

You need to have ttf-dejavu and wqy-microhei, both available from the official repositories, installed.

## Troubleshooting

- You may want to add `--hwaccel --drm` to ExecStart if you have problems with switching between Xorg and kmscon.

     ExecStart=/usr/bin/kmscon "--vt=%I" --seats=seat0 --no-switchvt --font-name Terminus --font-size 12 --hwaccel --drm

- As version 7, if you cannot control the audio, add your user to audio group. Be aware of the shortcomings of this choice.

Category:

- Terminal emulators