From:
Configure REISUB in FEDORA by doing:
$ grep -r -e kernel.sysrq /{etc,usr/lib}/sysctl.*
This command will output something like:
/usr/lib/sysctl.d/50-default.conf:# Use kernel.sysrq = 1 to allow all keys.
/usr/lib/sysctl.d/50-default.conf:kernel.sysrq = 16
According to the comments in the file /usr/lib/sysctl.d/50-default.conf we have to create a file /etc/sysctl.d/90-sysctl.conf with the line kernel.sysrq = 1
$ sudo echo "kernel.sysrq = 1" | sudo tee /etc/sysctl.d/90-sysrq.conf
Now, reboot the computer or apply the change with:
$ sudo systemctl restart systemd-sysctl.service
Verify with:
$ cat /proc/sys/kernel/sysrq
This should show 1
Now you can perform REISUB. To activate REISUB in Fedora, you can follow these steps:
1. Press and hold the Alt+PrtScn on your keyboard.
2. While holding the `Alt` key, press the following keys in sequence: `R`, `E`, `I`, `S`, `U`, `B`.
3. Release the `Alt` key after pressing the last key (`B`).
This key combination will trigger the REISUB sequence, which is a safe way to reboot your system without causing data loss. Each key in the sequence corresponds to a specific action:
- R: Switch the keyboard from raw mode to XLATE mode. We do this because the Desktop has stopped responding to the keyboard and we want to ensure any applications (like XOrg or Wayland) are not intercepting the keystrokes.
- E: Send the SIGTERM signal to all processes, allowing them to terminate gracefully.
- I: Send the SIGKILL signal to all processes, forcing them to terminate immediately.
- S: Sync all mounted filesystems, ensuring that all data is written to disk.
- U: Remount all filesystems in read-only mode, preventing any further changes to the disk.
- B: Reboot the system immediately without syncing or unmounting filesystems.
Make sure to use this key combination only when your system is unresponsive and you need to perform a forced reboot.
