Recovery mode: which image to fastboot?

[olf]

@nephros

Although I trust most of the Linux tools wouldn’t make much of a difference (see also: the terribly outdated version if btrfs-utils that shipped with the J1).

Well, these actually do (and shall) fit to the outdated btrfs in the outdated kernel the Jolla 1 uses.
See also the point below.

@nephros

However my suspicions lay more with the actual “recovery mode tools”, i.e. the fs check and factory reset functions of the recovery tool.

All filesystem-related tools should be used in a suitable version, i.e. at least the one a filesystem was created with, better the one it was last written to. Any newer version should work equally well (“upward compatibility”) when performing some recovery work, but mind that you will be back at older versions, when having recovered the SailfishOS installation proper and booting it.

Hence IMO your “TL;DR” for “recovery image release version versus installed SailfishOS release” might by:

1. Older than installed: NOT RECOMMENDED (reading stuff and altering config files is O.K., but a fsck, resizing a filsystem and LVM actions etc. should be avoided)
2. Same as installed: RECOMMENDED (theoretically the best)
3. Newer than installed: RECOMMENDED, but may expose issues in niche cases, which might be avoided by directly upgrading to the SailfishOS release (or any newer one) the recovery image was from