[root@localhost template_c]# mysql -uroot -p
Enter password:
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111)
[root@localhost template_c]# mysql -uroot -p
Enter password:
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111)
[root@localhost template_c]# mysql -uroot -p
Enter password:
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111)
[root@localhost template_c]# ps -ef |grep mariadb
root     11089  6586  0 18:24 pts/2    00:00:00 grep --color=auto mariadb
[root@localhost template_c]# systemctl restart mariadb.service
Job for mariadb.service failed because the control process exited with error code. See "systemctl status mariadb.service" and "journalctl -xe" for details.

出现以上错误，不难看出，mariadb没有启动成功，让我去查看​​systemctl status mariadb.service​​ 这个mariadb.service的服务状态。根据提示就进去了：

[root@localhost systemd]# systemctl status mariadb.service
● mariadb.service - MariaDB database server
   Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since 一 2017-06-26 18:29:27 CST; 8s ago
  Process: 11525 ExecStartPost=/usr/libexec/mariadb-wait-ready $MAINPID (code=exited, status=1/FAILURE)
  Process: 11524 ExecStart=/usr/bin/mysqld_safe --basedir=/usr (code=exited, status=0/SUCCESS)
  Process: 11496 ExecStartPre=/usr/libexec/mariadb-prepare-db-dir %n (code=exited, status=0/SUCCESS)
 Main PID: 11524 (code=exited, status=0/SUCCESS)

6月 26 18:29:26 localhost.localdomain systemd[1]: Starting MariaDB database server...
6月 26 18:29:26 localhost.localdomain mysqld_safe[11524]: 170626 18:29:26 mysqld_safe Logging to '/var/log/mariadb/mariadb.log'.
6月 26 18:29:26 localhost.localdomain mysqld_safe[11524]: 170626 18:29:26 mysqld_safe Starting mysqld daemon with databases from /.../mysql
6月 26 18:29:27 localhost.localdomain systemd[1]: mariadb.service: control process exited, code=exited status=1
6月 26 18:29:27 localhost.localdomain systemd[1]: Failed to start MariaDB database server.
6月 26 18:29:27 localhost.localdomain systemd[1]: Unit mariadb.service entered failed state.
6月 26 18:29:27 localhost.localdomain systemd[1]: mariadb.service failed.
Hint: Some lines were ellipsized, use -l to show in full.

服务启动失败，叫我去看mariadb的日志：

cat /var/log/mariadb/mariadb.log

结果如下：

InnoDB: Cannot continue operation.
170626 18:25:21 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended
170626 18:29:26 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
170626 18:29:26 [Note] /usr/libexec/mysqld (mysqld 5.5.52-MariaDB) starting as process 11801 ...
170626 18:29:26 [Warning] Can't create test file /var/lib/mysql/localhost.lower-test
170626 18:29:26 InnoDB: The InnoDB memory heap is disabled
170626 18:29:26 InnoDB: Mutexes and rw_locks use GCC atomic builtins
170626 18:29:26 InnoDB: Compressed tables use zlib 1.2.7
170626 18:29:26 InnoDB: Using Linux native AIO
170626 18:29:26 InnoDB: Initializing buffer pool, size = 128.0M
170626 18:29:26 InnoDB: Completed initialization of buffer pool
170626 18:29:26  InnoDB: Operating system error number 13 in a file operation.
InnoDB: The error means mysqld does not have the access rights to
InnoDB: the directory.
InnoDB: File name ./ibdata1
InnoDB: File operation call: 'open'.
InnoDB: Cannot continue operation.
170626 18:29:26 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended
170626 18:41:48 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
170626 18:41:48 [Note] /usr/libexec/mysqld (mysqld 5.5.52-MariaDB) starting as process 12394 ...
170626 18:41:48 [Warning] Can't create test file /var/lib/mysql/localhost.lower-test
170626 18:41:48 InnoDB: The InnoDB memory heap is disabled
170626 18:41:48 InnoDB: Mutexes and rw_locks use GCC atomic builtins
170626 18:41:48 InnoDB: Compressed tables use zlib 1.2.7
170626 18:41:48 InnoDB: Using Linux native AIO
170626 18:41:48 InnoDB: Initializing buffer pool, size = 128.0M
170626 18:41:48 InnoDB: Completed initialization of buffer pool
170626 18:41:48  InnoDB: Operating system error number 13 in a file operation.
InnoDB: The error means mysqld does not have the access rights to

说明mariadb的权限不够，不能写数据库，之前好像一不小心全改成www-data了，进去一看还真是，修改一下权限：
查看所有的用户和组，找出mariad所属的组和对应的用户。

cat /etc/group
 cat /etc/passwd

确定为用户和组分别为：​​mysql:mysql​​ ，修改一下权限：

chown -R mysql:mysql /var/lib/mysql
 chmod -R 755 /var/lib/mysql

启动mariadb：​​systemctl start mariadb.service​​ ,启动成功！登陆一下看看能不能登陆进去。

Can

已经搞好了，问题就是这么一步一步解决的。

报这个错还有一个原因，那就是mysql密码错了，解决方法如下：

​