Installationproblem

mariadb.service - MariaDB 10.3.8 database server
Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset:
Drop-In: /etc/systemd/system/mariadb.service.d
└─migrated-from-my.cnf-settings.conf
Active: failed (Result: exit-code) since Wed 2018-07-04 13:33:59 IST; 2min 35
Docs: man:mysqld(8)
https://mariadb.com/kb/en/library/systemd/
Process: 6576 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WS
Process: 6282 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR
Process: 6277 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START
Process: 6275 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/ru
Main PID: 6576 (code=exited, status=7)
Status: “MariaDB server is down”

Jul 04 13:33:56 kilinux-ideacentre-300S-11ISH systemd[1]: Starting MariaDB 10.3.
Jul 04 13:33:57 kilinux-ideacentre-300S-11ISH mysqld[6576]: 2018-07-04 13:33:57
Jul 04 13:33:57 kilinux-ideacentre-300S-11ISH mysqld[6576]: 2018-07-04 13:33:57
Jul 04 13:33:57 kilinux-ideacentre-300S-11ISH mysqld[6576]: 2018-07-04 13:33:57
Jul 04 13:33:59 kilinux-ideacentre-300S-11ISH systemd[1]: mariadb.service: Main
Jul 04 13:33:59 kilinux-ideacentre-300S-11ISH systemd[1]: Failed to start MariaD
Jul 04 13:33:59 kilinux-ideacentre-300S-11ISH systemd[1]: mariadb.service: Unit
Jul 04 13:33:59 kilinux-ideacentre-300S-11ISH systemd[1]: mariadb.service: Faile
~
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Have you tried
sudo service mysql restart