The ‘hostname’ command should return an FQDN, that is, fully qualified domain name. For example:
How do you set it up? Google search doesn’t return much of a useful information. And no, putting stuff into /etc/hosts doesn’t solve the issue. The solution is to edit /etc/nodename and put the FQDN in there and reboot.
echo foo.your.domain.com > /etc/nodename
shutdown -g0 -i6 -y
I have a hunch that reboot is unnecessary, but I haven’t figured out which service needs restarting for this change to take effect.