jenkins安装启动后，使用systemctl来进行进程监控
# systemctl enable jenkins
但是还是经常发生jenkins进程挂了，不会自动重启，通过systemctl查看状态为：
# systemctl status jenkins
● jenkins.service - LSB: Jenkins Automation Server
Loaded: loaded (/etc/rc.d/init.d/jenkins; bad; vendor preset: disabled)
Active: active (exited) since Tue 2019-09-24 18:52:26 CST; 1 months 1 days ago
Docs: man:systemd-sysv-generator(8)
Tasks: 0
Memory: 0B
查看日志没有任何异常，可能的原因如下：
Possibly the Linux kernel's oom-killer ("out-of memory killer") killed your JVM. It sends a SIGKILL signal to selected processes if the physical memory is no longer sufficient to accomodate all processes. Check that output of journalctl for lines containing the string oom-killer to confirm.
It is normal that the oom-killer strikes only after a certain period. Normally, Linux does not impose restrictions on the amount of virtual memory that a process requests (so your JVM can easily allocate 2 GiB of RAM on a 512 MiB system). However, if the process starts actually using the allocated memory (in your case: amount of used heap grows), then the kernel may find that the amount of physical memory is no longer sufficient. This is the point where the oom-killer will select a promising candiate process to be killed. Jenkins, as a non-system process that consumes a lot of memory, has very good chances to be the one that will be killed.
You can solve the situation by
- adding more physical memory to your system
- reducing JVM memory settings (e.g., smaller heap)
修改jenkins占用内存
# vi /etc/sysconfig/jenkins
JENKINS_JAVA_OPTIONS="-Xmx512m"
参考：https://stackoverflow.com/questions/42607771/jenkins-active-exited