Allow to select target slot for slots without bootname

[mkbanchi]

I need to have A+B slots without a bootname that i'd like to externally mark according to my logic (i have a custom install script for this). What i cannot figure out is the logic RAUC uses to select the slot to update and would be great if RAUC provided some way to force the target slot (in the same way write-slot does but without by-passing the update process starting from RAUC bundles).

Suppose i have the current apps partition mounted on /apps and the fallback one mounted on /bkp_apps.
I want always to update the slot mounted on /bkp_apps. Unfortunately there is no relation between the active one and the related device, the current partition is choosen at boot time).

I added allow-mounted in order to let the update process to not fail with "already mounted error" and my install script is correctly invoked. However when the update completes, i see that metadata (installation date, hashes, etc..) are obviously updated for the wrong target slot, the one that RAUC selects as the target slot for the update.

Am i missing something?
Could make sense to add possibilty to force an active slot of a specific type according to custom logic?

[ejoerns]

I need to have A+B slots without a bootname that i'd like to externally mark according to my logic (i have a custom install script for this).

Would the 'custom' bootloader backend match your requirements?

What i cannot figure out is the logic RAUC uses to select the slot to update and would be great if RAUC provided some way to force the target slot (in the same way write-slot does but without by-passing the update process starting from RAUC bundles).

See here for some details about how RAUC detects the slot it is booted from.

More details about the slot handling can be found in https://rauc.readthedocs.io/en/latest/basic.html#target-slot-selection

Maybe that answers parts of your question already?

Suppose i have the current apps partition mounted on /apps and the fallback one mounted on /bkp_apps. I want always to update the slot mounted on /bkp_apps. Unfortunately there is no relation between the active one and the related device, the current partition is choosen at boot time).

Does the inactive one actually need to be mounted?

For finding the devices, RAUC provides symlinks in /run/rauc. Maybe that's an option?

I added allow-mounted in order to let the update process to not fail with "already mounted error" and my install script is correctly invoked. However when the update completes, i see that metadata (installation date, hashes, etc..) are obviously updated for the wrong target slot, the one that RAUC selects as the target slot for the update.

A rauc status should tell you the slot RAUC identified as the active/booted one. Updating the slot that is selected as the target slot is of course the intended behavior.

Am i missing something? Could make sense to add possibilty to force an active slot of a specific type according to custom logic?

For the service, you can enforce the slot it assumes to be booted on, by setting --override-boot-slot.