+++ /dev/null
-Android A/B updates
-===================
-
-Overview
---------
-
-A/B system updates ensures modern approach for system update. This feature
-allows one to use two sets (or more) of partitions referred to as slots
-(normally slot A and slot B). The system runs from the current slot while the
-partitions in the unused slot can be updated [1].
-
-A/B enablement
---------------
-
-The A/B updates support can be activated by specifying next options in
-your board configuration file:
-
- CONFIG_ANDROID_AB=y
- CONFIG_CMD_AB_SELECT=y
-
-The disk space on target device must be partitioned in a way so that each
-partition which needs to be updated has two or more instances. The name of
-each instance must be formed by adding suffixes: _a, _b, _c, etc.
-For example: boot_a, boot_b, system_a, system_b, vendor_a, vendor_b.
-
-As a result you can use 'ab_select' command to ensure A/B boot process in your
-boot script. This command analyzes and processes A/B metadata stored on a
-special partition (e.g. "misc") and determines which slot should be used for
-booting up.
-
-Command usage
--------------
-
- ab_select <slot_var_name> <interface> <dev[:part_number|#part_name]>
-
-for example:
-
- => ab_select slot_name mmc 1:4
-
-or
-
- => ab_select slot_name mmc 1#misc
-
-Result:
-
- => printenv slot_name
- slot_name=a
-
-Based on this slot information, the current boot partition should be defined,
-and next kernel command line parameters should be generated:
-
- - androidboot.slot_suffix=
- - root=
-
-For example:
-
- androidboot.slot_suffix=_a root=/dev/mmcblk1p12
-
-A/B metadata is organized according to AOSP reference [2]. On the first system
-start with A/B enabled, when 'misc' partition doesn't contain required data,
-the default A/B metadata will be created and written to 'misc' partition.
-
-References
-----------
-
-[1] https://source.android.com/devices/tech/ota/ab
-[2] bootable/recovery/bootloader_message/include/bootloader_message/bootloader_message.h
projects / oweals / u-boot.git / blobdiff