Procsysrqtrigger

Procsysrqtrigger is a file located in the /proc filesystem of the Linux operating system. It is used to trigger system request (sysrq) commands, which are a set of special key combinations originally designed for the X86 architecture to perform various low-level operations on the system. These operations can include rebooting the system, syncing the filesystem, or killing all processes.

The sysrq commands are typically triggered by pressing the Alt and SysRq (or Print Screen) keys simultaneously, followed by another key to specify the command. However, the procsysrqtrigger file provides an alternative method to trigger these commands, which can be useful in situations where the keyboard is not accessible or when the system is unresponsive.

To use procsysrqtrigger, a user must have the appropriate permissions, as triggering certain sysrq commands can have significant impacts on the system. The file can be written to with the desired sysrq command as a string. For example, to trigger a system reboot, the user would write the string "b" to the file.

It is important to note that the availability and functionality of sysrq commands can be controlled through the sysrq kernel parameter, which can be set at boot time. Additionally, some distributions may disable sysrq commands by default for security reasons.

In summary, procsysrqtrigger is a file in the /proc filesystem that allows users with the appropriate permissions to trigger system request commands, which can perform various low-level operations on the Linux system. The availability and functionality of these commands can be controlled through the sysrq kernel parameter.