查看系统日志/var/log/mariadb/mariadb.log

190313 14:31:03 InnoDB: Database was not shut down normally!

InnoDB: Starting crash recovery.

InnoDB: Reading tablespace information from the .ibd files...

InnoDB: Restoring possible half-written data pages from the doublewrite

InnoDB: buffer...

190313 14:31:03 InnoDB: Waiting for the background threads to start

190313 14:31:04 Percona XtraDB (http://www.percona.com) 5.5.49-MariaDB-38.0 started; log sequence number 1597945

190313 14:31:04 [Note] Plugin 'FEEDBACK' is disabled.

190313 14:31:04 [ERROR] mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)

190313 14:31:04 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.

190313 14:31:04 [Note] Server socket created on IP: '0.0.0.0'.

190313 14:31:04 [ERROR] mysqld: Can't find file: './mysql/host.frm' (errno: 13)

190313 14:31:04 [ERROR] Fatal error: Can't open and lock privilege tables: Can't find file: './mysql/host.frm' (errno: 13)

190313 14:31:04 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended

190313 14:32:37 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

190313 14:32:37 [Note] /usr/libexec/mysqld (mysqld 5.5.52-MariaDB) starting as process 4335 ...

190313 14:32:37 InnoDB: The InnoDB memory heap is disabled

190313 14:32:37 InnoDB: Mutexes and rw_locks use GCC atomic builtins

190313 14:32:37 InnoDB: Compressed tables use zlib 1.2.7

190313 14:32:37 InnoDB: Using Linux native AIO

190313 14:32:37 InnoDB: Initializing buffer pool, size = 128.0M

190313 14:32:37 InnoDB: Completed initialization of buffer pool

提示没有找到plugin.frm，但是用find查找了一下，是存在的；

Can't find file: './mysql/plugin.frm'

谷歌了一下，是mysql的权限问题，如下为解决办法：

改变mysql目录的拥有者为mysql

chown –R mysql:mysql     /var/lib/mysql/

结果如下：

重启mariadb：systemctl restart mariadb.service

验证下结果：systemctl startus  mariadb.service

mariadb.service - MariaDB database server

Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; vendor preset: disabled)

Active: active (running) since Thu 2019-03-14 10:17:55 CST; 21s ago

Process: 15355 ExecStartPost=/usr/libexec/mariadb-wait-ready $MAINPID (code=exited, status=0/SUCCESS)

Process: 15326 ExecStartPre=/usr/libexec/mariadb-prepare-db-dir %n (code=exited, status=0/SUCCESS)

Main PID: 15354 (mysqld_safe)

CGroup: /system.slice/mariadb.service

├─15354 /bin/sh /usr/bin/mysqld_safe --basedir=/usr

└─15512 /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --log-error=/var/log/mariadb/mariadb.log --pid-file=/var/run/mariadb/m...

Mar 14 10:17:53 VMS94897 systemd[1]: Starting MariaDB database server...

Mar 14 10:17:53 VMS94897 mysqld_safe[15354]: 190314 10:17:53 mysqld_safe Logging to '/var/log/mariadb/mariadb.log'.

Mar 14 10:17:53 VMS94897 mysqld_safe[15354]: 190314 10:17:53 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

Mar 14 10:17:55 VMS94897 systemd[1]: Started MariaDB database server.