I'm thinking /etc/apt/sources.list.d/openmediavault-kernel-backports.list
should show deb http://archive.debian.org/debian/ jessie-backports main contrib non-free
instead of deb http://httpredir.debian.org/debian jessie-backports main contrib non-free
But I would like confirmation, so do not just do this without knowing what's going on.
This is the outcome after that change:
Ign file: InRelease
Ign file: Release.gpg
Ign file: Release
OK http://packages.openmediavault.org erasmus InRelease
Ign http://ftp.de.debian.org jessie InRelease
OK http://archive.debian.org jessie-backports InRelease
Ign http://ftp.de.debian.org jessie-updates InRelease
Ign file: Translation-de_DE
Ign file: Translation-de
Ign file: Translation-en
OK http://ftp.de.debian.org jessie Release.gpg
E: Release-Datei für http://archive.debian.org/debian/dists/jessie-backports/InRelease ist abgelaufen (ungültig seit 35 d 20 h 22 min 50 s). Aktualisierungen für dieses Depot werden nicht angewendet.
Alles anzeigen
I totally missed the EOL status of OMV3, my bad.
I hope that this problem does not block the omv-release-upgrade like in the other thread from Tii.
Are there any tips what to disable before starting the release upgrade? I have a few plugins from omv-extras 3 that are also available in the omv-extras 4 except for pyload.
What happens to a mergerfs unionfilesystem with 3 disk?
I'm scared. 
best regards
Max
EDIT: Found something that took my fear from upgrade, only issue is still Tii's thread about his problem during omv-release-upgrade.