Use current Ubuntu LTS 20.04 for docker image instead of 18.04

[1kastner]

Proposed change

Move from 18.04 to 20.04 in https://github.com/jupyterhub/the-littlest-jupyterhub/blob/18efee665aebd6c59334685eb9929f823ad649b0/integration-tests/Dockerfile - a nice side effect should be that the apt update should take less time since the image is a bit outdated.

Alternative options

Stick with the old version.

Who would use this feature?

Developers.

(Optional): Suggest a solution

Simply replace the Ubuntu version number

[manics]

Note the README currently says

The Littlest JupyterHub (TLJH) can run on any server that is running at least Ubuntu 18.04.

So the minimum supported version might also need to be bumped. Or perhaps both 18.04 and 20.04 should be tested?

[1kastner]

A good question. I would be happy with 20.04 as the current LTS version but some might prefer to also include 18.04. In that case it should also be tested.

[manics]

Another option might be to tag or branch the current version of TLJH, instruct people using 18.04 to use that tag/branch, and move all development to 20.04 with only major bug-fixes being backported?

[1kastner]

I just checked its lifecycle and it seems like 18.04 will be around for a while. Still I believe that it is reasonable to also test 20.04 and testing should be fast. Tests that take a too long will eventually be skipped. Your suggestion sounds reasonable to me.

[GeorgianaElena]

Hey @1kastner, @manics 👋

Thanks a lot for sharing ideas about this <3 This is definitely something that should happen.

There was another discussion about this some while ago here.
To summarize, the plan is keep the Ubuntu 18.04 support, by creating a separate branch for it and have the main branch default to Ubuntu 20.04.

I started the transition here: https://github.com/jupyterhub/the-littlest-jupyterhub/pull/635/files, but unfortunately I was a bit tight on time these days :( I will do my best to pick that up again this week. I would greatly appreciate any help reviewing or making the PR better ❤️

[1kastner]

Sure, I will have a look. Thanks a lot for linking these two issues!

[brianrusso]

FWIW I've installed it on 20LTS and didn't encounter any issues.

[deeplook]

Just curious about the status of this as I was trying to install TLJH following https://tljh.jupyter.org/en/latest/install/custom-server.html but it didn't like my Ubuntu 20.04.

[deeplook]

@GeorgianaElena @1kastner Any idea?

[1kastner]

@deeplook please open a new issue and provide a clear description of the error message etc. This issue here discusses the use of a docker image which is only supposed to be used by tljh developers.

[GeorgianaElena]

Solved by #710 🚀 🎉
Thanks @consideRatio!

[1kastner]

Thanks a lot!