I am a newb and this is my first error report. It appears reproducible.
If I change, key buffer setting in the mqsql configuration using thewebmin interface, it will change the /etc/mysql/my.conf file correctly AND insert the following line that means the mysql fails to start. I assume this is being accidentally written to the /etc/mysql/my.conf file.
The error that results is:
60319 22:25:01 [ERROR] /usr/sbin/mysqld: unknown variable 'set-variable=key_buffer=256M'
160319 22:25:01 [ERROR] Aborting
There is was another setting that was change that also seemed to insert this code that could in the my.conf file that could also not be processed on mysql restart.
Webmin appears to be inserting text into the my.conf file that doesn't belong there.
I sincerely apologise if this is an incorrect bug report.
Why MySQL version are you running there? It should be displayed in the mysql module in Webmin, at the top of the page.
Very sorry for delay. Just shifted countries.
MySQL version 5.5.47
Thanks - this will be fixed in the next webmin release.