How to enter recovery boot on R35.3.1

Robotics & Edge Computing Jetson & Embedded Systems Jetson Xavier NX
1

Hi,

Do you know how to recovery boot on R35.3.1 by Linux command? Thanks

2

Do you need this command?

sudo reboot --force forced-recovery

3

such command can’t work on Jetson Xavier NX platform. As your know, the ‘recovery’ partition on eMMC is listed as below, we need load ‘recovery’ image to enter recovery mode on R35.3.1.

/dev/mmcblk0p15: PARTLABEL=“recovery” PARTUUID=“4429b716-9b69-4fe8-b515-7e6b47955554”
/dev/mmcblk0p16: PARTLABEL=“recovery-dtb” PARTUUID=“0bcff437-eeb1-40ef-b86a-812d29b4760f”

5

Hi,

Recovery image and recovery mode are two different things.
If you need to enter recovery mode, then you need a jumper but not recovery image.
Can you please confirm it?

6

We need to boot to load ‘recovery’ image by Linux command, not your mentioned “recovery mode” by jumper to reflash image. Thanks.

7

Hi,

That’s fine. Just want to make sure because recovery image is seldom used.
Then you can do this to boot into the recovery image:

Press ESC to enter UEFI menu → then choose Device Manager → NVIDIA Configuration → L4T Configuration → L4T Boot Mode → choose Recovery Parition (it’s by default ExtLinux) → Save & Exit

8

Thanks, Dave. But This operation is not very convenient. I also notice UEFI efivars as follows:
/sys/firmware/efi/efivars/L4TDefaultBootMode-781e084c-a330-417c-b678-38e696380cb9
How can I set this recovery boot mode by Linux command? Thanks

9

Hi,

That’s feasible but a little tricky.

First, you know how the binary format of the variable looks like:

nvidia@tegra-ubuntu:/sys/firmware/efi/efivars$ hexdump -e '16/1 "%02X " "  |  "' -e '16/1 "%_p" "\n"' L4TDefaultBootMode-781e084c-a330-417c-b678-38e696380cb9
07 00 00 00 01 00 00 00                          |  ........

Then you need to turn off the write protection attribute of the varible with:

sudo chattr -i L4TDefaultBootMode-781e084c-a330-417c-b678-38e696380cb9

Finally, write new contents into the variable, which is shown in our document:
https://docs.nvidia.com/jetson/archives/r35.4.1/DeveloperGuide/text/SD/Bootloader/UEFI.html#customizing-the-default-boot-mode-in-l4tconfiguration-dtbo-in-the-bsp-directory
You need [ 03 00 00 00 ] for booting into the recovery kernel.

sudo su
printf “\x07\x00\x00\x00\x03\x00\x00\x00” > L4TDefaultBootMode-781e084c-a330-417c-b678-38e696380cb9

11

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