What is sysrq?

Do you have a situation where the server cannot log on through SSH or a local terminal, but the server can be pinged, and the digital keyboard lock can also respond to the key-hitting operation? In this case, what else have you done besides pressing the power supply or reset key? Have you ever thought that this situation may be restored? Have you ever thought about collecting more information to find out why the system is suspended? The above situation can be referred to as "an interrupted system suspension ". In other words, the system has stopped responding to most normal services for some reason, but the system can still respond to the keyboard key interruption request. In this case, a group of keys called sysrq will play a magical role.

Sysrq is often referred to as magic system request, which is defined as a series of key combinations. It is amazing because it is suspended in the system and most services are no longer able to respond. In addition, you can use a combination of buttons to complete a series of pre-defined system operations. With this function, you can not only restart a suspended server while ensuring disk data security, but also avoid data loss and file system checks after restart for a long time. It can also collect and use system memory, CPU task processing, process running status, and other system running information may even recover a server that has stopped responding without restarting.