I'm behind a firewall, so I can't access pool.ntp.org or Ubuntu's own time servers directly, and I'd like to change the time servers for my system. When googling, I find references to missing manpages like ntpd.conf(5) and ntpd(8), to a missing GUI for setting the time servers, and to a cron script (/etc/cron.daily/ntpdate) that doesn't seem to exist on my system. I've also found a reference to there being changes to ntpd.conf, so I'm hesitant to just create that file in /etc. How is one supposed to change the time servers in 11.10?