Cuirass stores GC roots for all the derivations of its jobsets under /var/guix/profiles/per-user/cuirass/cuirass (or similar).
The ‘delete-old-gc-roots’ periodically deletes these GC roots (which are not just derivations), but it’s supposed to keep GC roots to derivations that are queued: that was done in 55af0f70c0d4938b8eda777382bbc4d8f5698a37. Unfortunately, there’s ample evidence on berlin that GC roots of .drv currently queued get removed anyway. This causes workers to try in vain to substitute them, to eventually reject the build, which gets canceled by ‘remote-server’. Ludo’.
