| kmscon | |
| Developer: | David Herrmann |
| Discontinued: | yes |
| Latest Release Version: | 8 |
| Programming Language: | C |
| Operating System: | Linux |
| Genre: | System console |
| License: | ISC license |
Kmscon is a virtual console that runs in userspace which David Hermann created to replace the Linux console, a terminal built into the Linux kernel. Kmscon uses the KMS driver for its output, it is multiseat-capable, and supports internationalized keyboard input and UTF-8 terminal output. The input support is implemented using X keyboard extension (XKB). Development of Kmscon stopped in March 2015. There was a successor project called systemd-consoled, but this project was also later dropped in July 2015.
Kmscon supports printing the full set of Unicode glyphs and is not limited by console encoding as the Linux console. While the only hard dependency is udev, kmscon can optionally be compiled to use Mesa for hardware acceleration of the console, and the pango library for improved font rendering.
The adoption of XKB for input allows kmscon to accept the full range of available keyboard layouts for the X.Org Server and Wayland compositors for input and makes it possible to use the same layout both in graphical environment and in terminal.
See main article: article and Multiseat configuration.
The VT system in the Linux kernel dates to 1993 and does not implement out-of-the-box multiseat support. It supports up to 63 VTs, but only one VT can be active at any given time. This necessitates additional steps to configure multiseat support. kmscon/systemd-consoled will enable multiseat out-of-the-box.
If one seat's display server is running on VT 7 and another seat's display server is running on VT 8, then only one of these two seats can be used at a time. To use the other seat, a VT switch must be initiated.
To make all seats usable at the same time, there are a few options:
-sharevtsvt7 for user 1 and -novtswitch for all other users.In 2011, Jesse Barnes wrote in his blog about the possible userspace DRM-based implementation of the virtual terminal, that would dissolve the need for the Linux framebuffer and virtual terminal (VT) subsystems in the Linux kernel. Motivated by this blog post, David Herrmann implemented the basic functionality of virtual terminal.
In October 2013, terminal emulator state machine library, a state machine for DEC VT100–VT520 compatible terminal emulators, was split out of kmscon and made available separately. It was amended with wlterm, an example Wayland terminal emulator.