title: Failed to start MariaDB 10.2.16 database server
body: <p>When I have entered <code>systemctl status mariadb.service</code></p>
  
  <p>The output is:</p>
  
  <pre><code>mariadb.service - MariaDB 10.2.16 database server
     Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
    Drop-In: /etc/systemd/system/mariadb.service.d
             └─migrated-from-my.cnf-settings.conf
     Active: failed (Result: exit-code) since Tue 2018-07-17 13:53:46 +06; 24s ago
       Docs: man:mysqld(8)
             https://mariadb.com/kb/en/library/systemd/
    Process: 7342 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION (code=exited, status=1/FAILURE)
    Process: 7058 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] &amp;&amp; VAR= ||   VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ]   &amp;&amp; system
    Process: 7054 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
    Process: 7052 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
   Main PID: 7342 (code=exited, status=1/FAILURE)
     Status: "MariaDB server is down"
  
  Jul 17 13:53:43 munim-Inspiron-5548 systemd[1]: Starting MariaDB 10.2.16 database server...
  Jul 17 13:53:43 munim-Inspiron-5548 mysqld[7342]: 2018-07-17 13:53:43 139955312822464 [Note] /usr/sbin/mysqld (mysqld 10.2.16-MariaDB-10.2.16+m
  Jul 17 13:53:46 munim-Inspiron-5548 systemd[1]: mariadb.service: Main process exited, code=exited, status=1/FAILURE
  Jul 17 13:53:46 munim-Inspiron-5548 systemd[1]: Failed to start MariaDB 10.2.16 database server.
  Jul 17 13:53:46 munim-Inspiron-5548 systemd[1]: mariadb.service: Unit entered failed state.
  Jul 17 13:53:46 munim-Inspiron-5548 systemd[1]: mariadb.service: Failed with result 'exit-code'.
  </code></pre>
  
  <p>I have tried to login <code>mysql -u root -p</code> it shows </p>
  
  <pre><code>ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
  </code></pre>
  
  <p>Can anyone give me any suggestion?</p>