[Nexus 9 Original Android Development] yhvo2gt9:
vendor image is critical at time of OS installation

Hi there.

First of all, thanks so much for the official N9 build for Lineage. Really appreciate it.

I wanted to describe my experience this morning. I should start by saying that I am *not* a hacker, just an enthusiastic user. I can follow instructions, and have been using non-stock ROMs since Cyanogen 7.

I was upgrading from the most recent version of Cyanogen. Before I started, I upgraded to the latest TWRP. Then when booting into recovery, found that my decryption passphrase didn't work. I downgraded version by version until twrp-3.0.2-0-flounder.img which is apparently the latest that worked. After installing Lineage OS, I upgraded to the newest TWRP again.

More importantly, I wanted to point out that by following the instructions on the Lineage OS wiki for the Nexus 9, I almost got to the point of thinking I had bricked my device.

The main reason is that the instructions don't mention the Vendor image issue at all: https://wiki.lineageos.org/devices/flounder/install

After wiping, installing Lineage OS and GApps pico, I rebooted. When it got to the decryption passphrase, I got the pop-up warning about the Vendor image being mismatched. No problem, I thought, as I've seen that before on Cyanogen installs. I put in my decryption passphrase. The screen remained unchanged for a couple of minutes, then I got something I'd never seen before. A page notifying me that my passphrase was correct, but the system was corrupt, and an option to fix it (no other option was available except to force power-off). So I took that option and it rebooted into TWRP. It boots into recovery and apparently runs a script and reboots the system again. But the same issue occurred again, nothing was fixed.

No problem, I thought, I'll just power-off, boot into the bootloader, enter recovery, and try again. Except that after installing Lineage, I found that volume-down+power button no longer started the bootloader!!! I tried many times, but the best I got was the device booting into the system and getting the same problem where it said the system is corrupt. It was at this point that I thought I had bricked the device - can't boot into system, can't get to the bootloader, so can't get to the recovery.

After many attempts, I tried one last thing:

Boot into system

On the corruption notification screen, I pressed the button to "fix" the system corruption

when the device rebooted into Recovery to run the script, instead of entering my passphrase, I hit cancel. This cancelled the script process but left me in recovery. I then selected reboot -> bootloader. Success!!

I was then able to connect the device to my laptop and copy the Vendor image I had extracted from the official Google system image using

fastboot flash vendor vendor.img

I then rebooted, and everything worked fine.

So it seems that in this instance, it may be critical to install the Vendor image before the first reboot. In earlier versions of Cyanogen when I had a vendor image mismatch it never prevented the device from booting and I was able to update it later on.

In which case, whoever has access to the wiki on the Lineage website - could you add those instructions in?