To upgrade ubuntu off line or to reduce the amount of duplicate data downloaded when upgrading multiple ubuntu machines download the alternate install cd iso, mount it and do the upgrade as if you'd burnt the cd

1. Download alt cd iso http://ftp.citylink.co.nz/ubuntu-releases/11.04/

2. Mount the iso to /media/iso

   sudo mkdir /media/iso
   sudo mount ~/Downloads/ubuntu-11.04-alternate-i386.iso /media/iso -t iso9660 -o loop
   

3. Run the CDROM upgrade

   gksu /media/iso/cdromupgrade