Check if this helps to erase your emmc/micro-sd cards fully.
If using Linux on your PC
run ’ sudo lsblk ’ or
sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL
for more detailed info on your drives, partitions.
Find your micro-sd or emmc(if connected with a emmc to sd-card adaptor) drive name.
It should be /dev/sdb, /dev/sdc, /dev/sdd or /dev/sde usually since your internal hard-drive is /dev/sda
’ sudo wipefs /dev/sdb ’ (replacing /dev/sdb with your micro-sd card/emmc drive name)It will show your partition table.
Then run ’ sudo wipefs /dev/sdb -a ’
to wipe the partition tables so the micro-sd/emmc has no booting info.
Use an app like Etcher to write your Linux image to the micro-sd/emmc card.
Etcher will automatically use all the free space or reformat your micro-sd card/emmc and rewrite all the partitions for the Linux image you are writing.
Etcher can’t remove the partition tables on your drive, so that is why you need to run the above commands to do it manually.