Patch 'fstools' to set the overlay partition via a kernel parameter

For Developers
1

i can set the rootfs partition via the kernel parameter root=/dev/mmcblk0p<n>.

is there a similar way to set the rootfs_data partition?

2

No.

3

thanks.

strange... is the project against having it?

so the Spectrum SAX1V1K is an emmc device that has partitions:

  • kernel
  • rootfs (128 MiB)
  • rootfs_data (512 MiB)

and also has A/B versions of these partitions.

current port of this device does not support A/B updates and i want to add them to it. (it also has a buggy sysupgrade but that is another matter.)

here are my options:

  • leave it as it is (but fix the sysupgrade bug)
  • do A/B but leave the system using a single rootfs_data (which is a bit dangerous IMHO)
  • do A/B but store rootfs_data in a loop device behind rootfs, which will reduce rootfs_data from 512 MiB to around 75 MiB.
  • do A/B but store rootfs_data in a loop device behind rootfs, but store rootfs in the rootfs_data partition (requires uboot env changes and resetting data, and thus is an incompatible sysupgrade)
  • patch the fstools repo to support rootfs_data selection via kernel arg.

which would be favored by the project?

thanks again

4

Disclaimer, this is not my call (not an OpenWrt developer/ commiter), but I would suggest

75 MB is still plenty and this poses the least risk (and there is precedence, e.g. nbg6817).

5

thanks.

regarding the device, i PR'd a fix here:

i'd consider that as being worse current affairs. (given that i already implemented a recovery OS, A/B upgrades are not that important anymore.)

i'd probably go for adding the functionality to fstools. if that's not welcomed, i'd probably not bother with any changes.

6

and i also created a PR to allow selection of overlay, let's hope it gets merged: