[Reference] data partition layout

Note: I'm not using the /data prefix anywhere to make the text easier to read.

There are different layout versions. The version used is stored in /.layout_version

• 0: user data is stored in /media directly, all users have access to it
• 1: every user has it's own data in /media/<user_id>. OBB data is stored in /media/0/Android/obb
• 2/API17: like 1 but with OBB data being stored in /media/obb
• 3/API20: like 2 but with cacerts being stored in /misc/user/<user_id>

migration

0 -> 1

• move /media to /media.tmp
• create /media
• move /media.tmp to /media/0
• create /media/<user_id> for all existing users

if the process gets aborted you'll have a empty /media/0 directory but you'll still have /media.tmp which you can manually backup/move.

1 -> 2

• move /media/0/Android/obb to /media/obb

if the process gets aborted you'll have the old,unused OBB data in /media/0/Android/obb while /media/obb has already been created.

2 -> 3

• for all existing users:
  • create /misc/user/<user_id>
  • copy /keychain/cacerts-added to /misc/user/<user_id>/cacerts-added
  • copy /keychain/cacerts-removed /misc/user/<user_id>/cacerts-removed
• delete /keychain/cacerts-added
• delete /keychain/cacerts-removed