linux OTA

Simple EFI program allowing for safe OTA updates of Linux images using A/B-split booting.

EFI variable BOOTTOGGLE is made accessible in Linux through efivarfs interface, which is then set to "A" or "B" to boot from an updated image in-place, while allowing fallback for failed updates. An init script is used to set UPDATEFLAG and BOOTCOUNT to zero on successful boot.

Compiles on Linux using EDK. Couldn't get EDK working on macOS.

Boot parititon requires two startup scripts, boot_a.nsh and boot_b.nsh, which each boot separate versions of your boot image.

efi actions:

• if UPDATEFLAG == 0:
  • boot BOOTTOGGLE
• if UPDATEFLAG == 1:
  • if BOOTCOUNT == 0 (not yet attempted):
    • BOOTCOUNT = 1
    • boot BOOTTOGGLE
  • if BOOTCOUNT == 1 (boot from new image unsucessful):
    • BOOTTOGGLE = opposite script
    • UPDATEFLAG = 0
    • BOOTCOUNT = 0
    • boot modified BOOTTOGGLE

linux init script actions:

• if UPDATEFLAG == 0:

  • do nothing

• if UPDATEFLAG == 1 (boot must have been successful):

  • UPDATEFLAG = 0
  • BOOTCOUNT = 0

• BOOTTOGGLE is set during update