On 05/05/2023 02:16, Anand Jain wrote: > [...] >> >> https://lore.kernel.org/linux-btrfs/c702fe27-8da9-505b-6e27-713edacf723a@xxxxxxxxxx/ > > Confused about your requirement: 2 identical filesystems mounted > simultaneously or just one at a time? Latter works. Bugs were fixed. Hi Anand, apologies - in fact, in this old-ish thread I mentioned we need to mount one at a time, and this corresponds for the majority of the use case. BUT...it seems that for the installing step we require to have *both* mounted at the same time for a while, so it was a change in the requirement since last analysis, and this is really what we implemented here. > > Have you considered using the btrfs seed device feature to avoid > sacrificing 50% capacity? Create read-only seed device as golden image, > add writable device on top. Example: > > $ btrfstune -S1 /dev/rdonly-golden-img > $ mount /dev/rdonly-golden-img /btrfs > $ btrfs dev add /dev/rw-dev /btrfs > $ mount -o remount,rw /dev/rw-dev /btrfs > > To switch golden image: > > $ btrfs dev del /dev/rdonly-golden-img /btrfs > $ umount /btrfs > $ btrfstune -S1 /dev/rw-dev > Yeah, I'm aware that btrfs has some features that might fit and could even save space, but due to some requirements on Deck it's not possible to use them. I'll defer a more detailed response for John / Vivek / Ludovico, that are aware of the use case in a detail level I'm not, since they designed the installation / update path from the ground up. Cheers, Guilherme
