install-recovery.sh & applypatch

install-recovery.sh & applypatch

install-recovery.sh & applypatch

android/system/core/rootdir/init.rc：       

service flash_recovery          /system/etc/install-recovery         .sh        


                  class main        


                  oneshot

out/target/product/xxx/root/init.rc:

service flash_recovery          /system/etc/install-recovery         .sh        


                  class main        


                  oneshot

android\bootable\recovery\applypatch

android\build\tools\releasetools\ota_from_target_files

def          MakeRecoveryPatch(output_zip, recovery_img, boot_img):        


                  """Generate a binary patch that creates the recovery image starting        


                  with the boot image.  (Most of the space in these images is just the        


                  kernel, which is identical for the two, so the resulting patch        


                  should be efficient.)  Add it to the output zip, along with a shell        


                  script that is run from init.rc on first boot to actually do the        


                  patching and install the new recovery image.        


                   


                  recovery_img and boot_img should be File objects for the        


                  corresponding images.  info should be the dictionary returned by        


                  common.LoadInfoDict() on the input target_files.        


                   


                  Returns an Item for the shell script, which must be made        


                  executable.        


                  """        


                   


                  d          =          common.Difference(recovery_img, boot_img)        


                  _, _, patch          =          d.ComputePatch()        


                  common.ZipWriteStr(output_zip,          "recovery/recovery-from-boot.p"         , patch)        


                  Item.Get(         "system/recovery-from-boot.p"         ,          dir         =         False         )        


                   


                  boot_type, boot_device          =          common.GetTypeAndDevice(         "/boot"         , OPTIONS.info_dict)        


                  recovery_type, recovery_device          =          common.GetTypeAndDevice(         "/recovery"         , OPTIONS.info_dict)        


                   


                  sh          =          """#!/system/bin/sh        


         if ! applypatch -c %(recovery_type)s:%(recovery_device)s:%(recovery_size)d:%(recovery_sha1)s; then        


                  log -t recovery "Installing new recovery image"        


                  applypatch %(boot_type)s:%(boot_device)s:%(boot_size)d:%(boot_sha1)s %(recovery_type)s:%(recovery_device)s %(recovery_sha1)s %(recovery_size)d %(boot_sha1)s:/system/recovery-from-boot.p        


         else        


                  log -t recovery "Recovery image already installed"        


         fi        


         """          %          {          'boot_size'         : boot_img.size,        


                  'boot_sha1'         : boot_img.sha1,        


                  'recovery_size'         : recovery_img.size,        


                  'recovery_sha1'         : recovery_img.sha1,        


                  'boot_type'         : boot_type,        


                  'boot_device'         : boot_device,        


                  'recovery_type'         : recovery_type,        


                  'recovery_device'         : recovery_device,        


                  }        


                  common.ZipWriteStr(output_zip,          "recovery/etc/install-recovery.sh"         , sh)        


                  return          Item.Get(         "system/etc/install-recovery.sh"         ,          dir         =         False         )

5. ota.zip\recovery\etc\install-recovery.sh:

#!/system/bin/sh        


         if          ! applypatch          -         c MTD:recovery:         3586808         :a1bdc75a0eaa8faf855807c3b60c43dbcfb1400a; then        


                  log          -         t recovery          "Installing new recovery image"        


                  applypatch MTD:boot:         3776935         :         6cbe8dfacd08ba5cfa39b97e16de0d1f8176c0ed          MTD:recovery a1bdc75a0eaa8faf855807c3b60c43dbcfb1400a          3586808          6cbe8dfacd08ba5cfa39b97e16de0d1f8176c0ed         :         /         system         /         recovery         -         from         -         boot.p        


         else        


                  log          -         t recovery          "Recovery image already installed"        


         fi

Recovery will never overwrite itself, instead it will install a /system/etc/install-recovery.sh script to update recovery on the next bootup; this ensures that the system is always capable of booting into recovery even if the normal bootup fails. The install-recovery.sh script works by combining boot with a patch and writing the result to the recovery partition.