NewLine:
Is there a way to access the filesystem that is still on the flash, without removal of the SD card?
E.g. how can I access the /etc/config/fstab file on the Yun flash?
I found this tip on accessing the original flash drive while booted up on the external root: [OpenWrt Wiki] Extroot configuration
Basically, you boot up under the expanded drive, and add this to the end of /etc/config/fstab:
config mount
option target /overlay-boot
option device /dev/mtdblock3
option fstype jffs2
option options rw,sync
option enabled 1
option enabled_fsck 0
Next time you boot up under the expanded drive, the original file system on internal flash will be available under /overlay-boot. So to get to the original file system's fstab, use /overlay-boot/etc/config/fstab