does the software update keep downloaded files and packages if the
connection was lost?
There are two cases:
- If the connexion is interrupted during the downloading then after restarting the downloading process later it will continue normally if the files are not corrupted/altered.
- In case some of the downloaded files are altered during the transmission (downloading) process, then you need to read and follow this official documentation: PackageManagerTroubleshootingProcedure
does the update process (download and update) have to be in one
No. Not necessarily but:
- Do not stop the downloading process by yourself
- If your connexion is slow you are a little bit more prone to see errors during the transmission (downloading) process.
how can I list the downloaded packages and files for software update
on my computer?
Launch the Dash and search for Update Manager to see if there are updates to install:
If you do not launch the Update Manager, it will prompt itself each time there are new updates to ask you whether you want to update your packages or not.
can I download an off-line update package (.deb .gz or whatever) and
Yes. Depending on your version and release, you may search for the packages on Ubuntu Packages Search.
what can I do to successfully update ubuntu while having an unreliable
You may choose the package you want to update/install and download it somewhere (cybercafé, or using your university's Wi-Fi ...) and install it offline