| 1234567891011121314151617181920212223242526272829303132333435363738394041 |
- SD and MMC Device Partitions
- ============================
- Device partitions are additional logical block devices present on the
- SD/MMC device.
- As of this writing, MMC boot partitions as supported and exposed as
- /dev/mmcblkXboot0 and /dev/mmcblkXboot1, where X is the index of the
- parent /dev/mmcblkX.
- MMC Boot Partitions
- ===================
- Read and write access is provided to the two MMC boot partitions. Due to
- the sensitive nature of the boot partition contents, which often store
- a bootloader or bootloader configuration tables crucial to booting the
- platform, write access is disabled by default to reduce the chance of
- accidental bricking.
- To enable write access to /dev/mmcblkXbootY, disable the forced read-only
- access with:
- echo 0 > /sys/block/mmcblkXbootY/force_ro
- To re-enable read-only access:
- echo 1 > /sys/block/mmcblkXbootY/force_ro
- The boot partitions can also be locked read only until the next power on,
- with:
- echo 1 > /sys/block/mmcblkXbootY/ro_lock_until_next_power_on
- This is a feature of the card and not of the kernel. If the card does
- not support boot partition locking, the file will not exist. If the
- feature has been disabled on the card, the file will be read-only.
- The boot partitions can also be locked permanently, but this feature is
- not accessible through sysfs in order to avoid accidental or malicious
- bricking.
|
