

I have a long history of using various Ubuntu versions on my private SSH/HTTP/FTP/etc box and wonderful tool do-release-upgrade was already installed. I didn't actualy remember any major problems migrating from older versions of Ubuntu so I typed sudo do-release-upgrade and hit enter. Process of migrating from Jackalope to Koala went as smooth as a breeze although I was upgrading through an SSH session.
Logging in to the system was succesful after issuing a required reboot. I started screen (somehow all tweaks and bits like status line in a bottom of terminal windows were gone), created few virtual windows and ran usual programs such as rtorrent, Midnight Commander, silc, irssi, nano editor etc. Everything just worked...
... for a several days. I received IM from a friend of mine then. He was wondering why my FTP was down. Interesting part was that proftpd config files and default directories were there, but running sudo /etc/init.d/proftpd start|stop|restart failed everytime with no output whatsoever. It seemed like actual software just wasn't installed at all. sudo apt-cache search proftpd showed me that proftpd package is called by a different name - proftpd-basic - now (as opposed to proftpd in Ubuntu 9.04). sudo apt-get install proftpd-basic was next step but proftpd -n showed an error:
Failed binding to 0.0.0.0, port 21: Address already in use
Check the ServerType directive to ensure you are configured correctly.
After googling arround I found that possible solution for this problem can be switching FTP daemon from standalone to inetd mode in configuration file /etc/proftpd/proftpd.conf at ServerType directive. I edited corresponding line in a proftpd configuration file mentioned above and restarted server with sudo reboot. This helped bringing FTP service back to life.
I hope these simple tips and tricks will help you too!