Ability to use password file from some other installation

You can already keep home directories by choosing to mount an existing /home
partition and keep existing data on it.

Passwords are a difficult question. It's not entirely clear to me that it makes
sense to do this; there are a *lot* of edge cases involved.

The idea was more that if the home directory is on the same partition as the
root directory (so everything on one partition) of let's say your fedora
installation that you can just install ubuntu over fedora and that you keep your
files in the home directory and also keep your passwords and maybe some other
settings

Calling this one "confirmed", in that the wished-for behaviour doesn't happen.

It's an interesting idea... we could keep a copy of the old /etc/passwd and /etc/shadow, and then add real users (i.e. users with home directories) to the new system, keeping their existing password.

Seems like possibly a migration-assistant kind of thing, although m-a can generally only cope with migrating from partitions that you aren't about to erase. That said, I can't remember enough about its internals - would passwords be an exception to this general rule?

It could preseed the password data, which imho, would make the most sense as adding it as a checkbox would conflict with the password and password confirmation input boxes in the form.