Practical skills to prevent system processes from being accidentally killed

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 in the form of K * 2 ^ n, that is, the probability of killing them increases exponentially. In addition, the first process in the beginning of the day is 1) init is not included in the list, regardless of its oom_adj value. It turns out that only the process with the system resource management permission 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 dbus-daemon45956664root@gentux xiaosuo # cat /proc/4595/oom_score559root@gentux xiaosuo # echo -17 > /proc/4595/oom_adjroot@gentux xiaosuo # cat /proc/4595/oom_score0

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.

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