We should add to the start of hostname.err something like the following:
------ This file contains critical error messages and some important warnings from the mysqld server.
The reason for most errors should be found in the MySQL online manual at http://www.mysql.com/doc/E/r/Errorlog.html -------
The main problem with adding the text is that we should only do this when we start on a new 'hostname.err' file.
To get this working, I need to change that safemysqld doesn't redirect stderr and stdout, but instead send filenames to mysqld so that it can handle this itself.
The additional benefit is that after this FLUSH LOGS will also work on the .err file!