Methods To prevent system processes from being accidentally killed

Article Title: How to Prevent system processes from being accidentally killed. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

Linux memory management has a set of mechanisms: when the system memory overflows, it will choose one or several appropriate processes to kill to maintain the stable operation of the system. However, a machine is a machine after all. Although it tries its best to select the processes that are actually the culprit, it is difficult to determine which processes to choose to kill at this time, and sometimes errors will inevitably occur, or unfair. In the end, the system still becomes incomplete due to false positives, and even fails to run normally. At this time, it may be necessary to manually intervene and guide the system to make the right choice.

This behavior is controlled by adjusting/proc/[PID]/oom_adj in the corresponding directory of the process. The value of oom_adj is-17 ~ 15. When the oom_adj of a process is-17, the system will not kill it, -Between 16 and 15, the/proc/[PID]/oom_score value of the process increases exponentially (K * 2 ^ n). That is to say, the probability of their being killed increases exponentially. In addition, the first process (process no. 1) init is not in the kill list, regardless of its oom_adj value. In the past, only the process with system resource management permissions (CAP_SYS_RESOURCE) can adjust the oom_adj value. If the process is killed, no special permissions are required, we should not deprive it of suicide or the right of its owner to put it on a cliff.

The specific actions to prevent a process from being killed are as follows:

Root @ gentux xiaosuo # pgrep restart-daemon

4595

6664

Root @ gentux xiaosuo # cat/proc/4595/oom_score

559

Root @ gentux xiaosuo # echo-17>/proc/4595/oom_adj

Root @ gentux xiaosuo # cat/proc/4595/oom_score

0

Note: this technique is dangerous. unless you are sure that the process you prohibit is okay, do not try to make stupid settings. Otherwise, you will be at your own risk.