Magic SysRq Key
November 25, 2017 — 22:19

Author: silver  Category: linux  Comments: 0

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

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