Ubuntu Reference

Privileges command
sudo command – run command as root
sudo -s – open a root shell
sudo -s -u user – open a shell as user
sudo -k – forget sudo passwords
gksudo command – visual sudo dialog (GNOME)
kdesudo command – visual sudo dialog (KDE)
sudo visudo – edit /etc/sudoers
gksudo nautilus – root file manager (GNOME)
kdesudo konqueror – root file manager (KDE)
passwd – change your password