Updating ubuntu without internet
is a very broad term, and is generally taken to mean a program which you can run on your computer.However, such programs often need other resources to work.A package manager is an application which handles the downloading and installation of packages.Ubuntu includes a few package managers by default, and which one you use depends on how advanced the package management tasks are that you want to achieve.
Now that we either have the original signature of the machine because we were able to generate one at a distance or using a default signature that we created from the same USB installation key, we are able to generate a package of updates for those machines and send it over with the USB update disk for our appliance.
There are four Ubuntu software channels for each architecture - Main, Restricted, Universe and Multiverse. By default, only packages from Main and Restricted can be installed.
If you would like to install packages from Universe or Multiverse, see the Repositories page for instructions on how to do this. Be careful, though - some are not compatible with Ubuntu and using them may cause programs to stop working or may even cause serious damage to your installation.
A 'package', then, is essentially a collection of files bundled into a single file, which can be handled much more easily.
In addition to the files required for the program to run, there will be special files called for the program into that package.