How to use SysRq (Print Screen key)

( “REISUB” )

enable:

echo 1 > proc/sys/kernel/sysrq

permanently:

/etc/sysctl.d/local.conf
kernel.sysrq=1

To BREAK: CTRL+PAUSE (Serial)

ALT+SysReq+KEY
When logged in using SSH the SysRq may be accessible by writing to /proc/sysrq-trigger
echo s > /proc/sysrq-trigger

useful options:

• b: Immediately reboot the system, without unmounting or syncing filesystems
  echo b > proc/sysrq-trigger
• e: Send the SIGTERM signal to all processes except init (PID 1)
• f: Call oom_kill, which kills a process to alleviate an OOM condition:
• s: Sync all mounted filesystems:
• t: Output a list of current tasks and their information to the console:
• u: Remount all mounted filesystems in read-only mode
• w: Display list of blocked (D state) tasks
• space: Print a summary of available magic SysRq keys

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/Documentation/admin-guide/sysrq.rst
https://en.wikipedia.org/wiki/Magic_SysRq_key