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