Update the size of the system partition to >= 4 GiB
- document that a 8 GiB stick is required
- bump the default system partition size for newly installed Tails to 4 GiB on 8 GiB sticks, and to 8 GiB on sticks of 16 GiB or larger
- refuse installing a new Tails on a stick smaller than 8 GiB
- allow upgrading (by cloning) a legacy stick with a smaller (1.5 or 2.5 GiB) system partition when feasible; note that feasibility is a function of the size of data currently present on the source USB stick, and not of the size of its system partition
- provide useful messages when upgrade by cloning is impossible; we can mention the several available options, along with their pros/cons, i.e. “upgrade from ISO” (easier but has to be done every time) and “migrate to a new USB stick with a larger system partition and copy your persistent data” (painful, but then you’re done with it and get incremental upgrades for a while)
- follow-up bonus, if time allows: have Tails Upgrader mention the “migrate to a new USB stick with a larger system partition” too when incremental upgrade is impossible due to a too small system partition; would be nice, but I don’t want to block on that; it can be handled on #11628 (closed).
The corresponding work will be tracked as subtasks.
Feature Branch: feature/12705-bump-system-partition-size, installer:feature/12705-bump-system-partition-size