suddenly cannot connect database

[david4321]

when i try go surf sentora login page , it say cannot connect database.
maybe I did not shutdown linux normally yesterday

I try to reboot my vps but still not working.
when i type mysql in ssh, it said
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

How can I fix it?
Thanks

Critical Error: [0100] - Unable to connect or authenticate to the Sentora database (sentora_core).

We advice that you contact the server administrator to ensure that the database server is online and that the correct connection parameters are being used.

http://forums.sentora.org/showthread.php...mysql.sock
I try found this post but still can't fix it.
df -h 

Filesystem               Size  Used Avail Use% Mounted on

/dev/mapper/centos-root   48G   40G  7.6G  85% /

devtmpfs                 486M     0  486M   0% /dev

tmpfs                    497M     0  497M   0% /dev/shm

tmpfs                    497M  6.6M  490M   2% /run

tmpfs                    497M     0  497M   0% /sys/fs/cgroup

/dev/vda1                497M  354M  144M  72% /boot
tmpfs                    100M     0  100M   0% /run/user/0

sudo service mysqld restart
Failed to restart mysqld.service: Unit not found.

mv /var/lib/mysql/mysql.sock /var/lib/mysql/mysql.sock.bak
service mysqld start
not working

systemctl start 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.

● mariadb.service - MariaDB database server

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

   Active: failed (Result: exit-code) since Thu 2017-04-06 10:13:18 JST; 4s ago

  Process: 4191 ExecStartPost=/usr/libexec/mariadb-wait-ready $MAINPID (code=exited, status=1/FAILURE)

  Process: 4190 ExecStart=/usr/bin/mysqld_safe --basedir=/usr (code=exited, status=0/SUCCESS)

  Process: 4162 ExecStartPre=/usr/libexec/mariadb-prepare-db-dir %n (code=exited, status=0/SUCCESS)

 Main PID: 4190 (code=exited, status=0/SUCCESS)


systemctl status mariadb.service

Apr 06 10:13:15 mtserver.melon-tea.com systemd[1]: Starting MariaDB database server...

Apr 06 10:13:15 mtserver.melon-tea.com mysqld_safe[4190]: 170406 10:13:15 mysqld_safe Logging to '/var/log/mariadb/mariadb.log'.

Apr 06 10:13:15 mtserver.melon-tea.com mysqld_safe[4190]: 170406 10:13:15 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

Apr 06 10:13:18 mtserver.melon-tea.com systemd[1]: mariadb.service: control process exited, code=exited status=1

Apr 06 10:13:18 mtserver.melon-tea.com systemd[1]: Failed to start MariaDB database server.

Apr 06 10:13:18 mtserver.melon-tea.com systemd[1]: Unit mariadb.service entered failed state.
Apr 06 10:13:18 mtserver.melon-tea.com systemd[1]: mariadb.service failed.


some log file of /var/log/mariadb/mariadb.log
170406 10:13:44 [ERROR] Aborting



170406 10:13:44  InnoDB: Starting shutdown...

170406 10:13:45  InnoDB: Shutdown completed; log sequence number 348406146

170406 10:13:45 [Note] /usr/libexec/mysqld: Shutdown complete



170406 10:13:45 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended

170406 10:26:09 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

170406 10:26:09 [Note] /usr/libexec/mysqld (mysqld 5.5.52-MariaDB) starting as process 1514 ...

170406 10:26:09 [Warning] Can't create test file /var/lib/mysql/mtserver.lower-test

170406 10:26:09 InnoDB: The InnoDB memory heap is disabled

170406 10:26:09 InnoDB: Mutexes and rw_locks use GCC atomic builtins

170406 10:26:09 InnoDB: Compressed tables use zlib 1.2.7

170406 10:26:09 InnoDB: Using Linux native AIO

170406 10:26:09 InnoDB: Initializing buffer pool, size = 128.0M

170406 10:26:09 InnoDB: Completed initialization of buffer pool

170406 10:26:09 InnoDB: highest supported file format is Barracuda.

170406 10:26:09  InnoDB: Waiting for the background threads to start

170406 10:26:10 Percona XtraDB (http://www.percona.com) 5.5.49-MariaDB-38.0 started; log sequence number 348406146

170406 10:26:10 [Note] Plugin 'FEEDBACK' is disabled.

170406 10:26:10 [Note] Server socket created on IP: '::1'.

170406 10:26:10 [ERROR] Can't start server : Bind on unix socket: Permission denied

170406 10:26:10 [ERROR] Do you already have another mysqld server running on socket: /var/lib/mysql/mysql.sock ?
170406 10:26:10 [ERROR] Aborting

[Me.B]

Ha "Percona XtraDB " this is not the official setup.

How you did get it there? Did you try to force upgrade the default db?

M B