解决Monit启动监控进程消失monit.service failed.

Monit监控软件启动时无法启动监控。

Monit启动监控进程消失提示monit.service failed.

在CWP控制面板（CWP7）安装Monit监控软件后，Monit启动监控进程消失，出现提示：monit.service failed.

值得注意的是，已经尝试启用过了systemctl enable monit

[root@stage-web-1 vagrant]# systemctl status monit
monit.service - Pro-active monitoring utility for unix systems
Loaded: loaded (/usr/lib/systemd/system/monit.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Thu 2017-06-01 16:37:00 UTC; 6min ago
Process: 1131 ExecStop=/usr/bin/monit quit (code=exited, status=1/FAILURE)
Process: 1079 ExecStart=/usr/bin/monit -I (code=exited, status=1/FAILURE)
Main PID: 1079 (code=exited, status=1/FAILURE)

Jun 01 16:37:00 stage-web-1 systemd[1]: Started Pro-active monitoring utility for unix systems.
Jun 01 16:37:00 stage-web-1 systemd[1]: Starting Pro-active monitoring utility for unix systems...
Jun 01 16:37:00 stage-web-1 monit[1079]: Error opening the log file '/var/www/html/nfs/monit/stage-web-1.log' for writing -- No such file or directory
Jun 01 16:37:00 stage-web-1 systemd[1]: monit.service: main process exited, code=exited, status=1/FAILURE
Jun 01 16:37:00 stage-web-1 monit[1131]: Error opening the log file '/var/www/html/nfs/monit/stage-web-1.log' for writing -- No such file or directory
Jun 01 16:37:00 stage-web-1 systemd[1]: monit.service: control process exited, code=exited status=1
Jun 01 16:37:00 stage-web-1 systemd[1]: Unit monit.service entered failed state.
Jun 01 16:37:00 stage-web-1 systemd[1]: monit.service failed.

事实说明，它/var/www/html/nfs是通过NFS安装到网络驱动器的文件夹。

Monit是在NFS之前启动的，因此该文件夹尚不存在，从而导致monit错误Error opening the log file '/var/www/html/nfs/monit/stage-web-1.log' for writing -- No such file or directory。

如何解决Monit启动监控进程消失monit.service failed.？

解决方法是编辑/lib/systemd/system/monit.service：

[Unit]
Description=Pro-active monitoring utility for unix systems
After=network.target

[Service]
Type=simple
ExecStart=/usr/bin/monit -I
ExecStop=/usr/bin/monit quit
ExecReload=/usr/bin/monit reload

[Install]
WantedBy=multi-user.target

并添加nfs.service到该After后面。最终结果如下所示：

[Unit]
Description=Pro-active monitoring utility for unix systems
After=network.target nfs.service

[Service]
Type=simple
ExecStart=/usr/bin/monit -I
ExecStop=/usr/bin/monit quit
ExecReload=/usr/bin/monit reload

[Install]
WantedBy=multi-user.target

Monit监控程序现在可以在启动时，成功启动了。