Cold reboot linux after desktop freeze

cold reboot linux after desktop freeze
If all else fails, one can “Raise The Elephant”

there are special  SysRq key sequences (Alt+SysRq+?) that the Linux kernel handles specially.

If your Linux box freezes and won’t yield to any other key-commands, you can try one particular key sequence before a hard reboot.

The key sequence is remembered with the mnemonic:
Raising Elephants Is So Utterly Boring
• Alt+SysRq+R switch keyboard to ‘raw’ mode
• Alt+SysRq+E send SIGTERM (termination) signal to all processes except mother init
• Alt+SysRq+I send SIGKILL signal to all processes, a little more aggressive
• Alt+SysRq+S sync all filesystems to prevent data loss
• Alt+SysRq+U remount filesystems as read-only
• Alt+SysRq+B forcefully reboot

https://unix.stackexchange.com/questions/31818/what-to-do-when-a-linux-desktop-freezes