不能satart mariadb服务器。 systemctl状态mariadb.service给我这个信息，但我不明白我该如何解决它？
* mariadb.service - MariaDB database server
Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Thu 2018-06-14 11:58:04 MSK; 4min 0s ago
Process: 14150 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION (code=exited, status=7)
Process: 13996 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= || VAR=`/usr/bin/galera_recovery`; [ $? -eq
Process: 13991 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
Process: 13987 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
Main PID: 14150 (code=exited, status=7)
Jun 14 11:58:00 cs3 mysqld[14150]: 2018-06-14 11:58:00 140176199283264 [Note] InnoDB: 128 rollback segment(s) are activ
Jun 14 11:58:00 cs3 mysqld[14150]: 2018-06-14 11:58:00 140176199283264 [Note] InnoDB: Waiting for purge to start
Jun 14 11:58:01 cs3 mysqld[14150]: 2018-06-14 11:58:01 140176199283264 [Note] InnoDB: Percona XtraDB (http://www.perco
Jun 14 11:58:01 cs3 mysqld[14150]: 2018-06-14 11:58:01 140176199283264 [Note] Plugin 'FEEDBACK' is disabled.
Jun 14 11:58:01 cs3 mysqld[14150]: 2018-06-14 11:58:01 140176199283264 [ERROR] /usr/sbin/mysqld: unknown variable 'log_
Jun 14 11:58:01 cs3 mysqld[14150]: 2018-06-14 11:58:01 140176199283264 [ERROR] Aborting
Jun 14 11:58:04 cs3 systemd[1]: mariadb.service: Main process exited, code=exited, status=7/NOTRUNNING
Jun 14 11:58:04 cs3 systemd[1]: Failed to start MariaDB database server.
Jun 14 11:58:04 cs3systemd[1]: mariadb.service: Unit entered failed state.
Jun 14 11:58:04 cs3 systemd[1]: mariadb.service: Failed with result 'exit-code'.