Patching one of our spare servers this morning and ran into a couple of issues. The first was a complaint in the service status:
mariadb.service: Referenced but unset environment variable evaluates to an empty string: MYSQLD_OPTS, _WSREP_NEW_CLUSTER
Which was fixed by running systemctl edit mariadb.service and adding
Environment="MYSQLD_OPTS=" Environment="_WSREP_NEW_CLUSTER="
This is just a warning, and does not affect anything. Naturally it should be fixed though. Potential fix posted in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1105029
The second was from the error log which stated that the service was unable to read /etc/mysql/rest/keyfile.passwd, which turned out to be a permissions error on /etc/mysql/rest which was 600 and not 700 (I checked the other servers and theirs were also 600 so I guess it's the fix for MDEV-36229 which caused that)
Now the server starts but it core dumps almost immediately. Systemctl status shows:
This is the main problem, and I don't have any insight to that, just wanted to comment on the service file variables.