If you have an Ubuntu machine without an internet connection,you can try Keryx to download all updates on another Windows/Linux PC and keep the Ubuntu machine updating off-line via an USB.

Keryx is a free and open source tool for easily managing packages on offline Debian based computers including support for Ubuntu and Linux Mint. It provides an easy graphical interface to help install and upgrade software.

With Keryx,you can download Ubuntu packages on your work PC (with Windows or Linux system) and save in an USB.Then go back to the Ubuntu machine,plug-in the USB and install the packages off-line.

How it works:

1. Download Keryx and extract ,this package include executable program for Linux and Windows (“keryx” in linux folder and “keryx.exe” in win32 folder).

2.Download project package and extract.It includes several folders,copy and paste appropriate one into the USB stick.(I chose “lucid-64bit-default” for my Ubuntu 10.04 amd64 machine.)

3.Plug-in the USB stick on the PC with internet connection.Run keyrx (linux/keryx on Linux,or win32/keryx.exe on Windows),then choose the folder (“lucid-64bit-default” in my case) you just pasted into the USB.It will starts updating source list,and then you can get the update packages via “Get Updates” button.

4.Finally,plug-in the USB in Ubuntu machine without internet.Run the “keryx” file in linux folder and choose “lucid-64bit-default” and start updating off-line.

Note: You’d better save the keryx.tar.gz you downloaded in step1 into USB,because it is useful in both Ubuntu machine and another machine with internet connection.

Read official tutorial on how Keryx works