Jetson TX2 update terrorrt accidentally upgraded the system to L4T 35, causing a series of integration problems, and how to do it (the boot disk is an SSD case)

• ​System environment: Ubuntu18.04
• Jetson tx2 architecture: aarch64
• JetPack 4.6.3
• L4T version is 32.7.3

The upgraded version is 35.3 by mistake:

deb https://repo.download.nvidia.com/jetson/common r35.3 main
deb https://repo.download.nvidia.com/jetson/t180 r35.3 main

Then I didn’t pay attention and kept filling in Yes, then sent it. The symptoms are as follows: the gui interface cannot be opened, and there are start kernel and Failed to start nvpmode server errors. Remounting the ssd still doesn't solve the problem.

It is obvious that it is caused by apt dist-upgrade.​ 

Check the mounting status.​ 

Here are some solutions to think about:

• Issues involving using a custom carrier board and using an SD card for booting. Here's a summary of the steps you took and the problems you encountered:

1. default setting:

   • Using Seeed's custom carrier board, either JetPack is pre-installed or a new JetPack is flashed on the eMMC.
   • Insert the SD card and follow Seeed's instructions to enable it.

2. Flash JetPack OS to SD card:

   • Flash JetPack OS from eMMC to SD card. This involves copying the contents of the eMMC to the SD card and updating the /boot/extlinux/extlinux.conf file to set the "root" entry to the SD card (/dev/mmcblk1p1).

3. Upgrade the kernel:

   • Executesudo apt upgrade to upgrade the kernel on the SD card.

4. Startup issues:

   • During the boot process, the device attempts to load old kernel files on the eMMC, causing the boot to fail.

5. Solution steps:

   • Connect to the device using Putty and SSH.
   • Mount eMMC.
     • Change the root entry in /mnt/boot/extlinux/extlinux.conf back to eMMC (/dev/mmcblk0p1).
     • Reboot the device.
     • The device should now be able to boot from eMMC again.
     • 执行sudo apt upgrade.
     • Enable the SD card again.
     • Change the root entry in/boot/extlinux/extlinux.conf back to the SD card (/dev/mmcblk1p1).
     • The device should now be able to boot from the SD card.sudo -s mount /dev/mmcblk0p1 /mnt

•  I have also tried the above method using ssd mounting but it was of little use. Mounting refers to the blog for another method After restoring the extlinux.conf file to eMMC, first back up the entire SSD. Because the system configuration will not change due to the disk mapping system, wait until the backup is restored to format the entire SSD, and then configure the source eMMC. Copy the system and then apt-upgrade, and finally migrate the entire software in the SSD we backed up back. I am currently implementing this plan (I have failed with this plan, so I can only brush emmc honestly)
• Because it does not involve system compatibility issues in eMMC, I feel that it is not necessary to flash the phone as a last resort. Because at that time, a lot of systems were configured and it took a lot of time. If I can do it without flashing, I will not flash the phone. If it is flashing, compare the following files in the SSD boot disk after flashing to see if you can restore the settings.