Install fails when apt can't update

[jbicha]

What happened?

The install fails when the system has an IP Address through a network connection but the network connection does not actually include Internet access.

What was expected?

Checking whether the network has Internet connectivity may be a good idea.

However, it is possible for a machine to have Internet connectivity but still not be able to reach the apt repos. This should not fail the install; it should skip the steps that require an apt update or apt install of things not provided on the ISO.

Steps to reproduce

No response

Additional context

Originally reported with logs at https://launchpad.net/bugs/2037008

[seb128]

subiquity is doing mirror probing to verify that the connection is working and if it's not it flags an error. The desktop frontend doesn't do anything today to handle those cases.

There was a discussion in 'FO088 - More robust APT mirrors management in Subiquity' about what we should do from the desktop installer perspective, our options are basically

• error out (which is what the installer does today and what the report is about). It's not user friendly because it's subiquity hitting an error, which leads to an ubuntu-bug dialog and an error label on the installer but without explanation of the issue

• display a some UI informing the user about the issue and giving the choice to retry or use offline mode

• automatically fallback to do an offline installation. The drawback is that it means the installed system content might not match the selected option (e.g if the extra codecs option was selected those need to come from internet which isn't possible in offline mode so they would be missing despite the fact that the box was checked)

I'm unsure what's best. My input on the spec at the time was to let the installation fail but that's not a nice user experience so in retrospect I wonder if we should just fallback to offline mode and let the installed system not match the selected options...

[bittin]

Had this issue earlier today too when trying to install the 1th December 2023 image and the apt mirror at ftp.acc.umu.se had not synced up yet discussed this with @jpnurmi some months ago in the Ubuntu Flutter Discord too so would be good if it can fallback to another mirror or use archive.ubuntu.org when the mirrors are not synced yet?