John said:
The majority of my problems appear to have come from
things like
deprecated options in various package config files that, rather
than being nicely ignored in new versions, cause stuff to grind to
a screeching halt, or packages not being correctly installed that
would be required for new ways of doing various things.
The only big config file change I can remember is Dovecot, where it's
a completely new system.
The other two issues were that mysql-server got removed and needed to
be reinstalled, and although it doesn't seem to be in the Debian
release notes's list of obsolete packages, sysklogd has gone. So if
you use that for syslogd, you need to install inetutils-syslogd instead.
More details in an email here on the 21st May last year.
Ian