As you probably know, Debian 6.0 alias Squeeze has been released on 6-2-2011. So, i upgraded my ISPConfig2 testing server to see if i can expect any problems, at time i will upgrade my ISPConfig2 production server. During my upgrate from Debian Lenny to Squeeze, i noticed that there was only one problem: It was not possible to start proftpd with /etc/init.d/proftd. So i did some investigation: On Squeeze, to install proftpd, you need to do "apt-get install proftpd-basic" instead of "apt-get install proftpd". So i did: "apt-get --purge remove proftpd", after that i did an "apt-get install proftpd-basic". After that i modified the configuration file /etc/proftpd/proftpd.conf as described here: http://www.howtoforge.com/perfect-server-debian-lenny-ispconfig2-p5 The everything was up and running again. Hope this information helps others who want to upgrade their Debian Lenny server with ISPConfig2 as well.