I know I could use initrd/initramfs to do whatever needed, but I would like to avoid this option, if possible.
I need to have a "normal" working rootfs (on an SD card of an embedded system, if it matters). If, for any reason, booting won't succeed (e.g.: kernel is unable to cleanly mount this system) it should attempt booting from a "recovery" rootfs (SquashFS on Flash) which will be responsible for restoring the "normal" filesystem and restart.
Is something like this available without resorting to initramfs?
Reason why I don't want initrd/initramfs is because of limitations in Flash size.