What size should the A and B partitions be? I can’t think of any reasonable way to size them that is also future-proof. Android had the same problem, and they solved it by using device mapper. Unfortunately, I doubt LVM meets our security goals, which means a whole new userspace implementation would be required. That would not be fun, especially since a bug would require a reinstall to correct. Other image-based Linux distros generally don't have this problem because they use filesystem or ostree snapshots, rather than separate partitions. Chromium OS has a whole team of paid developers, so I think they can deal with constraints a bit better than we can :). One horrifying worst-case option is to add a file on the user data partition, create a loop device based on it, and then add it to the dm-verity table. I really don't want to do that if there is any other option, though. -- Sincerely, Demi Marie Obenour (she/her/hers)