Wednesday, 21 June 2017

On eMMC boot partitions

In the eMMC usually you would find boot partitions which are called high-speed boot according to the Micron. These are physical partitions where you can keep your bootloader and have a physical write protect provided by the chip. This is one of the ways you can lock down the bootloader.

If you have booted Linux kernel you would find the information of the partitions in the /dev/mmcblkXbootN so for eg in my beaglebone black I have the eMMC at /dev/mmcblk1 and the two partitions at /dev/mmcblk1boot0 and /dev/mmcblk1boot1.

The write protect information of these partitions is present in the file /sys/block/mmcblk1boot0/force_ro. To remove the write protect one can simply do a

echo 0 > /sys/block/mmclbk1boot0/force_ro

We can then create partition information using fdisk and also create a file system using ext2fs.

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