Created attachment 711151 [details]
Installer upgrade fails to find 42.1 installation on volume "fs_sys", subvolume
"sysroot"

When doing system upgrades using the DVD (or via USB media), the installer
failed to find the previous installations of opensuse on btrfs volumes. An
offline upgrade is thus not possible.

In one case, the upgrade was from opensuse 42.1 to 42.2. The previous
installation had the root fs mounted from a subvolume "sysroot".

In another case, the upgrade was from 13.2 to 42.2. The previous installation
had the root fs in the root of the volume (no subvolumes).

The installer finds the volumes and identifies them as btrfs. However, it
cannot see any installations.

The online upgrade via zypper dup worked without major problems for both
systems.

The offline upgrade was the first choice because of the information in the wiki
documentation.
The wiki page https://en.opensuse.org/SDB:System_upgrade is very vague
regarding the difference between online and offline update. It states 
"It [the online upgrade] does not do all of the cleanup and maitanence that an
offline DVD Upgrade does." It is unclear what this actually means.
Also, contrary to the wiki page, the release notes of opensuse 42.2 state that
an update from 13.2 to 42.2 is possible and supported.

A possible fix could be to allow for manual selection of volume and
subvolume(s).
If a particular naming scheme (e.g. with @/) has to be used, it should be 
documented precisely.