wbinfo -u. If you don't do this, you can't use sudo, pwd won't work (a lot of stuff breaks, essentially). So, to hack around it, I wrote a script called keepActiveDirectoryAlive and put it in
sleep 30s; wbinfo -u;
Easy! This probably isn't the best or most efficient way to do this, so if you have a better idea, I am more than welcome to suggestions.
I set this to start with GNOME in my Sessions. I also had to set
wbinfo -uto run in
/etc/rc.local(though I seem to remember Ubuntu/Debian ignoring this file) so that I can login through GDM. It seems to be working as expected.