mysql - Status: "MariaDB server is down" -

hope can me:

i have many sites running on server , using mariadb. when do:

sudo service mysql restart 

i get:

job mariadb.service failed because control process exited  error code. see "systemctl status mariadb.service" , "journalctl -xe"  details. 

systemctl status mariadb.service

    mariadb.service - mariadb 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 thu 2017-09-14 03:16:51 utc; 1min 6s ago     process: 13247 execstart=/usr/sbin/mysqld $mysqld_opts $_wsrep_new_cluster $_wsrep_start_position (code=     process: 13086 execstartpre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && var= ||   var=`/usr/bin/gale     process: 13070 execstartpre=/bin/sh -c systemctl unset-environment _wsrep_start_position (code=exited, s     process: 13033 execstartpre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, st    main pid: 13247 (code=exited, status=1/failure)    status: "mariadb server down"    cgroup: /system.slice/mariadb.service            └─3803 /usr/sbin/mysqld 

sudo journalctl -xe

   sep 14 03:35:51 ubuntu systemd[1]: failed start mariadb database server.    -- subject: unit mariadb.service has failed    -- defined-by: systemd    -- support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel    --     -- unit mariadb.service has failed.    --     -- result failed.    sep 14 03:35:51 ubuntu systemd[1]: mariadb.service: unit entered failed state.    sep 14 03:35:51 ubuntu sudo[13566]: pam_unix(sudo:session): session closed user root    sep 14 03:35:51 ubuntu systemd[1]: mariadb.service: failed result 'exit-code'.    sep 14 03:35:52 ubuntu sshd[13753]: failed password root 123.183.209.136 port 38816 ssh2    sep 14 03:35:52 ubuntu sshd[13753]: received disconnect 123.183.209.136 port 38816:11:  [preauth]    sep 14 03:35:52 ubuntu sshd[13753]: disconnected 123.183.209.136 port 38816 [preauth]    sep 14 03:35:52 ubuntu sshd[13753]: pam 1 more authentication failure; logname= uid=0 euid=0 tty=ssh ruser    sep 14 03:36:34 ubuntu sshd[13756]: connection closed 123.183.209.136 port 60477 [preauth]    sep 14 03:36:36 ubuntu postfix/pickup[12161]: 703aa5c0c5: uid=0 from=<root>    sep 14 03:36:36 ubuntu postfix/cleanup[12162]: 703aa5c0c5: message-id=<20170914033636.703aa5c0c5@ubuntu.me    sep 14 03:36:36 ubuntu postfix/cleanup[12162]: warning: 703aa5c0c5: write queue file: no space left on dev    sep 14 03:36:36 ubuntu postfix/pickup[12161]: warning: maildrop/5152f5c0c4: error writing 703aa5c0c5: queu    sep 14 03:37:17 ubuntu sshd[13760]: received disconnect 123.183.209.136 port 25567:11:  [preauth]    sep 14 03:37:17 ubuntu sshd[13760]: disconnected 123.183.209.136 port 25567 [preauth]    sep 14 03:37:36 ubuntu postfix/pickup[12161]: 7764b5c0c5: uid=0 from=<root>    sep 14 03:37:36 ubuntu postfix/cleanup[12162]: 7764b5c0c5: message-id=<20170914033736.7764b5c0c5@ubuntu.me    sep 14 03:37:36 ubuntu postfix/cleanup[12162]: warning: 7764b5c0c5: write queue file: no space left on dev    sep 14 03:37:36 ubuntu postfix/pickup[12161]: warning: maildrop/5152f5c0c4: error writing 7764b5c0c5: queu    sep 14 03:37:47 ubuntu sudo[13765]:      bob : tty=pts/0 ; pwd=/home/bob ; user=root ; command=/bin/journa    sep 14 03:37:47 ubuntu sudo[13765]: pam_unix(sudo:session): session opened user root bob(uid=0)    lines 1238-1265/1265 (end) 

i don't want lose db. should next?

many thanks

this df gives me:

   filesystem     1k-blocks     used available use% mounted on    /dev/root       49362256 46854648         0 100% /    devtmpfs         2019828        0   2019828   0% /dev    tmpfs            2021768        0   2021768   0% /dev/shm    tmpfs            2021768    17968   2003800   1% /run    tmpfs               5120        0      5120   0% /run/lock    tmpfs            2021768        0   2021768   0% /sys/fs/cgroup    tmpfs             404356        0    404356   0% /run/user/1000    tmpfs             404356        0    404356   0% /run/user/0 

see first filesystem (/dev/root) 100% full! , there no other volumes mounted besides tmpfs volumes. mariadb trying write disk starts up, , can't, gives , shuts down.

you have figure out what's filling disk, , prune can. example, guess i'd start looking in http server logs, since host many sites on server. i've seen many servers filled disk space letting httpd log months , months.

in future, might want provision server more 1 disk volume, if 1 volume fills doesn't interfere other volumes.

also consider automating log rotation.

if culprit disk space usage not logs, mariadb data directory, might need additional disk volume immediately, , move mariadb content before can bring sites online.

unless can find little bit of other stuff elsewhere on server can delete , make enough space short while.