journalctl查看指定服务并监控该服务的事实服务状态
[root@localhost system]# journalctl -f -u mariadb.service #打印最近一次mariadb的服务动作，然后-f继续只监听该mariadb服务动作实时输出
-- Logs begin at Fri 2020-02-28 17:51:37 CST. --
Feb 29 02:16:28 localhost.localdomain systemd[1]: Starting MariaDB database server...
Feb 29 02:16:29 localhost.localdomain systemd[1]: mariadb.service: control process exited, code=exited status=1
Feb 29 02:16:29 localhost.localdomain systemd[1]: Failed to start MariaDB database server.
Feb 29 02:16:29 localhost.localdomain systemd[1]: Unit mariadb.service entered failed state.
Feb 29 02:16:29 localhost.localdomain systemd[1]: mariadb.service failed.
Feb 29 02:17:00 localhost.localdomain systemd[1]: Starting MariaDB database server...
Feb 29 02:17:00 localhost.localdomain systemd[1]: mariadb.service: control process exited, code=exited status=1
Feb 29 02:17:00 localhost.localdomain systemd[1]: Failed to start MariaDB database server.
Feb 29 02:17:00 localhost.localdomain systemd[1]: Unit mariadb.service entered failed state.
Feb 29 02:17:00 localhost.localdomain systemd[1]: mariadb.service failed.