Documentation/admin-guide/sysrq.rst

9 It is a 'magical' key combo you can hit which the kernel will respond to
87 	This way, all characters will be processed. E.g.::
99 ``b``	    Will immediately reboot the system without syncing or unmounting
102 ``c``	    Will perform a system crash and a crashdump will be taken
109 ``f``	    Will call the oom killer to kill a memory hog process, but do not
114 ``h``	    Will display help (actually any other key than those listed
115             here will display help. but ``h`` is easy to remember :-)
126 ``m``	    Will dump current memory info to your console.
130 ``o``	    Will shut your system off (if configured and supported).
132 ``p``	    Will dump the current registers and flags to your console.
134 ``q``	    Will dump per CPU lists of all armed hrtimers (but NOT regular
140 ``s``	    Will attempt to sync all mounted filesystems.
142 ``t``	    Will dump a list of current tasks and their information to your
145 ``u``	    Will attempt to remount all mounted filesystems read-only.
161             will be printed to your console. (``0``, for example would make
175 when you would try to login. It will kill all programs on given console,
186 useful when you want to exit a program that will not let you switch consoles.
196 shell that provides no graceful shutdown -- it will ensure your data is
201 running system's point of view, they will be remounted read-only. The remount
205 kernel messages you do not want to see. Selecting ``0`` will prevent all but
206 the most urgent kernel messages from reaching your console. (They will
249 the header ``include/linux/sysrq.h``, this will define everything else you need.
251 handler function you will use, B) a help_msg string, that will print when SysRQ
252 prints help, and C) an action_msg string, that will print right before your
256 ``register_sysrq_key(int key, const struct sysrq_key_op *op_p);`` this will
260 which will remove the key op pointed to by 'op_p' from the key 'key', if and
287 console, even though it will appear in the dmesg buffer, and be accessible
292 Should you require the output on the console channel then you will need