How can I reformat microSD cards that were created read-only?
Solution 1:
The SD card should be unmounted before attempting format.
You will probably need to use mkdosfs
for FAT16
mkdosfs /dev/sdb2 -F16
or for FAT32
mkdosfs /dev/sdb2 -F32
Solution 2:
I have found more information on this:
SD cards have a physical lock, to write protect the card. MicroSD cards don't have the lock, but the SD adapter has it, and it can lock-unlock the card.
So, try to put the card in an adapter and slid the lock a few times, leaving it on unlocked.