When starting mysql on Centos servers with a custom data directory you might get an error similar to the following:
2014-10-15 10:23:56 17081 [Warning] Can't create test file /database/mysql/localhost.lower-test
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3 Answers
If your chmod and chown settings are already correct you might need to look into selinux.
This page explains how to configure selinux for mysql:
https://blogs.oracle.com/jsmyth/entry/selinux_and_mysql
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If selinux is disabled. Then you need to check your chmod/chown settings. Another thing you can check is if your harddrive is full. Also check out Uwe's answer above. It could be helpful in your case.– HalukMar 8, 2018 at 12:48
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None of the above. The new MariaDB 10.1 adds some weird protection to Systemd service file. I'm gonna write a FIX i discovered as an answer.– LukaMar 8, 2018 at 13:16
If you tried fixing ownership and permissions.
chown -R mysql:mysql /new-path/mysql
chmod 0755 /new-path/mysql
And you do not have SELinux enabled but you still have a problem.
All you need to do is to edit /usr/lib/systemd/system/mariadb.service
ProtectSystem=full
ProtectHome=true
and undefine those variables (setting it to false won't work)
ProtectSystem=
ProtectHome=
And reload daemon
systemctl daemon-reload
After I did this it finally worked. Interesting is that this occurs only with MariaDB 10.1 Those variables are not existent for earlier versions. Recently I have found this bug:
https://jira.mariadb.org/browse/MDEV-13896
EDIT:
Since this configuration gets overwritten after a MariaDB update, I have found a permanent fix to avoid any further downtime because of this.
cp /usr/lib/systemd/system/mariadb.service /etc/systemd/system/mariadb.service
Then I made changes here instead
vi /etc/systemd/system/mariadb.service
That's it :)
When running on CentOS 7, check out the systemd unit files which may prevent writing to / protect non-MySQL directories like /home.
The unit files lives in /usr/lib/systemd/system/mariadb.service.
