Ubuntu – How does the Ubuntu upgrade process work


How does Ubuntu upgrade seamlessly to a newer distribution, while the operating system is still running? I'm upgrading from 10.10 to 11.04, and I've upgraded several times before, and it's as simple as running update-manager -d and downloading and installing them, then rebooting.

How exactly does this work though? How is the upgrade manager able to update the operating system while it is still in use?

Best Answer

From my experience I would assume that while packages and modules are running they are held in memory and don't refer back to their copy on the hard drive much. You can see this if you run a program in ubuntu and then remove the related packages while its running. It will keep running, but if you close it, you can't restart it.

I would assume the same happens with a distribution upgrade. All of the packages related to the original version of ubuntu are still running even though they have been removed and replace with the new ones, so when they are finally stopped on a system restart, the new packages take over.