Magic SysRq key

Principal among the offered commands are means to forcibly unmount file systems, kill processes, recover keyboard state, and write unwritten data to disk.

On distributions that do not include a textmode command,[clarification needed] the key sequence Ctrl+Alt+F1 may be able to force a switch to a text console.

While the magic SysRq key was originally implemented as part of the kernel's keyboard handler for debugging, the functionality has been also exposed via the proc filesystem and is commonly used to provide extended management capabilities to headless and remote systems.

[11] The Linux daemons sysrqd[12] and tcpconsole[13] provide a method of accessing SysRq features over a TCP connection after authenticating with a plain-text password.

The hangwatch[14] daemon will invoke pre-configured SysRq triggers when system load average exceeds a certain threshold.

[15] Additionally, a SysRq command can be invoked from a Xen paravirtual console by sending a break sequence Ctrl+O followed by the desired key.

[19][20] IBM Power Systems servers can invoke the Magic SysRq feature using Ctrl+O followed by the desired key from the Hardware Management Console.

IBM mainframe partitions can invoke the Magic SysRq feature using ^+- followed by the desired key on 3270 or HMC.