KDE Linux/Recover from boot failures

It can be quite distressing when a computer fails to boot up normally! Here are some recovery mechanisms:

Roll back to an older OS image

If the boot failure started happening after you updated the system, rolling back to the older version will generally fix it.

To do this:

1. Power on the machine.
2. When you see the OS image chooser (in white text in the center of the screen, against a black background), press the down arrow key once to navigate to the prior OS image.
3. Press the Enter key to boot into it.

If this fixes the issue, please report it at https://invent.kde.org/kde-linux/kde-linux/-/issues/, and attach the output of running journalctl --boot -1 --no-pager in a terminal window.

Disable systemd extensions

If you have any Systemd extensions active, and the boot failure started happening after you updated the content in any of them, this could be the cause. Temporarily disabling the extension should resolve the issue.

To do this:

1. Press Ctrl+Alt+F3 repeatedly while booting up, until you end up on a black screen with some white text on top (this is known as a "Virtual Terminal", or "VT").
2. Type your username and press Enter.
3. Type your password and press Enter. This will log you into a textual login session in the VT.
4. Type sudo systemd-sysext unmerge and press Enter. This will disable the extension.
5. Type reboot and press Enter.

Hopefully the system will start up normally now.