General Linux stuff

To find out disk space usage
df
sudo du -sk /


NAT/Firewall
taken from Ubuntu wiki


edit /etc/iptables.up.rules
and add line along the lines of
-A PREROUTING -s 195.188.208.0/255.255.255.0 -i eth1 -p tcp -m tcp --dport 10000 -j DNAT --to-destination 172.16.0.10:3389
This will allow 195... to access port 10000 which nat's to .10 on 3389

then sudo iptables-restore < /etc/iptables.up.rules
to load new rule.

Ubuntu iptables howto
nice frontend for iptables (command line)