I put Jessie on a laptop. 'hostname -f' said it couldn't do it (don't remember the error message, but it was, essentially, "Oops").
The instructions on the 'Net for fixing the missing domain name in Jessie were the same as they've always been: put the fully qualified domain name (fqdn) with the IP in /etc/hosts. They were already there, so I moved them to the top, like the picture on the web, and rebooted. Didn't work. I saw another suggestion from somewhere else: put the domain name in /etc/resolv.conf. I did that and got my 'hostname -f' working. 'hostname --ip-address' worked too. The problem with that is that there's a line at the top of the resolv.conf: "Generated by NetworkManager." So I went to /usr/sbin, moved NetworkManager to NetworkManagerqw, and created an executable NetworkManager shell script that put the right info in resolv.conf. A reboot wiped the file and put that "Generated..." line back at the top with nothing else in the file. The file is rewritten from scratch on boot. 'strings' tells me that the "Generated..." string is in /usr/sbin/NetWorkManagerqw. I spent a long time trying to find out where the faulty resolv.conf was being created and how to either get it out of the way so I could just write it myself, or at least get it to put the right info in the file. (Failed) This is what we're supposed to use for servers on the Internet? That error would kill the iptables packet filters on all my servers if I put Jessie on them. Now far be it from me to throw more gasoline on the systemd flames, but this is unacceptable. System V was certainly a mess too, with all those files being sourced into the init.d files. But it did bring up the kernel and a few daemons, and 'hostname -f' worked. If I were the powers that be at Debian, I'd have done a little work cleaning up System V instead of going to what seems to be buggy, a little too smart for its own good, and next to impossible to decipher, init software. Debian has a well deserved reputation for being some of the most stable software available. Sid is supposed to be broken, and that's fine -- it's alpha and its bugs get fixed as it slides down the hill. But when it gets to stable it's supposed to work. Real good, and all the time. Thank you for your attention... -- Glenn English