{{tag>mysql mariadb replication}}

====== mysql/mariadb troubleshooting ======
===== mount namespacing =====

If you get this error

<code>
Jul 14 13:00:20 mariadb systemd[1]: Starting MariaDB 10.3.15 database server...
Jul 14 13:00:21 mariadb systemd[1296]: mariadb.service: Failed to set up mount namespacing: Permission denied
Jul 14 13:00:21 mariadb systemd[1296]: mariadb.service: Failed at step NAMESPACE spawning /usr/sbin/mysqld: Permission denied
Jul 14 13:00:21 mariadb systemd[1]: mariadb.service: Main process exited, code=exited, status=226/NAMESPACE
Jul 14 13:00:21 mariadb systemd[1]: mariadb.service: Failed with result 'exit-code'.
Jul 14 13:00:21 mariadb systemd[1]: Failed to start MariaDB 10.3.15 database server.
</code>

The workaround is to override the mariadb.service file

<code>
cat <<EOF >/etc/systemd/system/mariadb.service.d/override.conf
[Service]
ProtectSystem=off
PrivateDevices=false
ProtectHome=false
EOF
</code>

If running a container in Proxmox you can also enable Nesting from web gui container > Options > Edit > Features > Nesting

===== mariadb won't start =====
If starting with ''systemctl start mariadb'' times out, try checking if the instance is part of Galera cluster. It might be that other instances need to be started as well.


===== [ERROR] Error reading packet from server: Client requested master to start replication from impossible position ( server_errno=1236)  =====

  replication from impossible position; the first event 'mysql-bin.004225' at 14311389, the last event read from 'mysql-bin.004225' at 4, the last byte read from 'mysql-bin.004225' at 4.'

Happened when master server crashed. The error above showed on slave. Solution is to start replication from the next binlog file after the one in error above.

First stop slave:

  MariaDB [(none)]> STOP SLAVE;

Change binlog and start slave:

  MariaDB [(none)]> CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.004226', MASTER_LOG_POS=4;
  MariaDB [(none)]> START SLAVE;
  MariaDB [(none)]> show slave status \G

====== Tested on ======
  * 

====== See also ======

====== References ======
  * https://mariadb.com/docs/server/server-management/starting-and-stopping-mariadb/what-to-do-if-mariadb-doesnt-start
  * https://mariadb.com/resources/blog/client-requested-master-to-start-replication-from-impossible-position/
  * https://serverfault.com/questions/1184180/mysql-replication-1236-requested-master-to-start-replication-from-impossible-pos