Running Raspbian Buster. I have a loopback mount defined in fstab (bind option) where directory A is looped in as B. I have another service started later (with systemd After=local-fs.target) that turns directory A into an OverlayFS in ZRAM. Effectively that means the original (lower fs in terms of OverlayFS) A is made available as C and A now is the name of the virtual/combined FS. Problem now is that B still points to where A pointed before that OverlayFS mount occured (C, effectively). But I want it to point to to what A is now.
How could I resolve that ordering problem?
Note I cannot move the OverlayFS mount to happen before local-fs.target as it in turn obviously requires that at least local disks are already mounted. Can I maybe somehow set an option to exclude loopback mount(s) from happening when local-fs.target is reached, then add another unit file to run after my OverlayFS is up ? Or can I only remove them from fstab and explicitly mount them via unit file at a late stage?