OK I admit it I used the file manager in webmin to change mine.
The owner on my system is root and the group is zimbra
so would change into the directory where file is
chgrp redo.log zimbra
That way the group is zimbra
then use chmod to set the file permissions to read and write for the zimbra group cant rembember how to do that but this will help
http://catcode.com/teachmod/