Starting MariaDB 10.1 causes timeout. Syslog says:

Apr  5 20:55:53 megis systemd[1]: Starting MariaDB 10.1.38 database server...
Apr  5 20:55:53 megis mysqld[6892]: 2019-04-05 20:55:53 140074458918016 [Note] /usr/sbin/mysqld (mysqld 10.1.38-MariaDB-0ubuntu0.18.04.1) starting as process 6892 ...
Apr  5 20:55:54 megis kernel: [  980.249533] kauditd_printk_skb: 2 callbacks suppressed
Apr  5 20:55:54 megis kernel: [  980.249535] audit: type=1400 audit(1554486954.089:38): apparmor="DENIED" operation="sendmsg" info="Failed name lookup - disconnected path" error=-13 profile="/usr/sbin/mysqld" name="run/systemd/notify" pid=6892 comm="mysqld" requested_mask="w" denied_mask="w" fsuid=121 ouid=0
Apr  5 20:57:23 megis systemd[1]: mariadb.service: Start operation timed out. Terminating.

There can be more lines where AppArmor says

audit(1554487043.725:40): apparmor="DENIED" operation="sendmsg" info="Failed name lookup - disconnected path" error=-13 profile="/usr/sbin/mysqld"

Some notes in the net suggest that you should set the TimeoutSec=infinity in the systemd configuration, but this did not help in my case. I had to disable the AppArmor for /usr/sbin/mysqld. It wasn’t enough to put it to complain mode. Here are the instructions:

Get apparmor-utils

If you can’t execute “sudo aa-disable” you have to install the AppArmor utilities:

sudo apt install apparmor-utils

Create AppArmor profile for MariaDB

By default the AppArmor profile for /usr/sbin/mysqld is empty which causes “aa-disable” to fail. Add following lines to “/etc/apparmor.d/usr.sbin/mysqld”:

/usr/sbin/mysqld {
}

Disable AppArmor for /usr/sbin/mysqld

After this say:

sudo aa-disable /usr/sbin/mysqld