I have a Pi 4 I need to restore booting from USB

Question

I have a raspberry Pi 4 that was fine for months if not a couple years.

It boots from attach USB storage on NVME.

I did a rpi-update, and now it isn't booting.

Now before everyone says don't do that. I have done this 40+ time successfully without any issues of any kind.

I plug the USB device into another computer, and checked the file system they all check out and there are no errors on any of them.

Question? How do I restore booting from USB?

I get 4 or 5 long green flashes following by another 4 or 5 short/fast flashes of the green led. Red is solid.

Answer 1

rpi-update installs the unstable and untested version of the OS with the latest changes. It is expected to break every now and then, especially on non-standard configurations (such as booting from something else than the SD card).

Rolling back an update could be done by reverting actions from /var/log/apt/history.log, however, you need a system with working apt to do so. If you can't boot, you might be able to chroot into your system from a bootable system which has apt installed. I would expect you need to restore raspberrypi-bootloader and raspberrypi-kernel packages.

If you can't revert the changes, I'm afraid you'll have to restore a backup if you have one, or start from scratch.

Answer 2

So the answer here is:

1. Make another bootable SD or USB card with what OS you used.
2. Update it to match your broken device
3. Copy all files except cmdline.txt from the FAT16 partition to FAT 16 partition on broken device.
4. umount both devices
5. unplug device from step #1
6. Reboot and pray

I screwed up a second time and overwrote cmdline.txt which contains the partition UUID so I had to manually change that back to the correct UUID.

Everything is fine now.