What is proc sysrq trigger

But rest assured, the current keyboard generally supports pressing 3 or more keys at the same time. It can be seen from the file name that the two are related. Therefore, the two lines of commands first enable the SysRq function, and then use the 'b' command to restart the computer immediately. Tech Community Register Log in. FaceBook Share. Restart the server 1. So how do you use the SysRq key? If the kernel is really in strife, you may not ever get the OK or Done message I generally sync s , umount u , then reboot b when my system locks.

The loglevels 0 - 9 are useful when your console is being flooded with kernel messages you do not want to see. Selecting 0 will prevent all but the most urgent kernel messages from reaching your console. That happens to me, also. Oh, and by the way, you exit showkey by not typing anything for ten seconds. This is in case the slot has been overwritten since you registered it. This key table has a number of operations registered into it at compile time, but is mutable, and 2 functions are exported for interface to it:.

Of course, never ever leave an invalid pointer in the table. Null pointers in the table are always safe. Sysrq output is subject to the same console loglevel control as all other console output. As a specific exception the header line from the sysrq command is passed to all console consumers as if the current loglevel was maximum.

On a busy, fully booted system, the output may be tens of thousands of lines long. The output should be much shorter than that of the " t " command key because not all processes are printed out.

Useful if a memory-related issue is suspected. A kernel core dump will be stored if kdump is enabled, see [3]. When getting debugging data, it is a good idea to send the command keys repeatedly with the exception of " c " with at least several seconds in between the commands keys. In this way, the state of the system at different points in time is captured. There are also command keys for rebooting a machine with as minimal an impact as possible:.

This lessens the chance of data loss. There is a mnemonic for remembering the order of the above command keys:. Server with SSH:. Log into the machine with ssh. Server with serial console only:. It is often necessary to resort to using the serial console when a system starts misbehaving.

Otherwise, Sysrq keys can also be sent over a serial line by sending a break followed by a command key within 5 seconds. Note: The type of terminal you have will define how to 'send break', e. The top bar of the console holds a tool for sending SysRq keys. Join Our Community. Go to Customer Center. All Products. Cloud-native Transformation Orchestrate containerized applications.