Trying to install grapheneos on a refurbished Pixel 6, and "fastboot flashing unlock" hangs "< waiting for any device >.

OEM unlocking is enabled.
USB debugging is enabled.

With Android running, "adb devices" sees the Pixel, displays:
List of devices attached
[serial number] device

When I boot to the bootloader, "adb devices" does not see the Pixel, but "fastboot devices" displays:
[serial number] fastboot

But "fastboot flashing unlock" displays:
< waiting for any device >

And nothing happens. Same result with any other fastboot action command, e.g. "fastboot reboot bootloader".

Android Debug Bridge version 1.0.41
Version 33.0.3-8952118

fastboot version 33.0.3-8952118

I successfully flashed a Pixel 3a with Ubuntu Touch a few days ago, so this appears to be specific to the Pixel 6, or perhaps this particular Pixel 6.

Has anyone encountered this problem and fixed it?

Resolved. Contrary to the grapheneos installation instructions, setting /sys/bus/usb/drivers_autoprobe to zero was the problem. When I set it to 1, "fastboot flashing unlock" worked.

On Linux, GNOME has a bug causing compatibility issues with the installation process. It wrongly detects the phone in fastboot mode or fastbootd mode as being an MTP device and claims exclusive control over it. This will block the install process from proceeding. You can run the following command to work around it:

echo 0 | sudo tee /sys/bus/usb/drivers_autoprobe
After installing, you can undo this by rebooting or by running the following command:

echo 1 | sudo tee /sys/bus/usb/drivers_autoprobe

5 months later

Thank you! I am typing this out and being descriptive to help with the SEO for the next person searching for a solution to this problem, as it took me a while to find your post...

I followed the Command Line installation guide on Jul 12, 2023 in ArchLinux and faced this issue. I am installing GrapheneOS on a Pixel 7. What I could see was that the ./flash_all.sh script would hang with no output, and using htop I could see that the script was stuck running the command "fastboot getvar product". Running the command "fastboot getvar product" would show me the < waiting for any device > message.

Setting /sys/bus/usb/drivers_autoprobe back to 1 did fix this issue for me. During the actual installation you can see the output immediately appear.

4 months later

I had the exact same issue while following the CLI guide with Ubuntu 22.04 for a Pixel 8, and indeed, the solution was to not set /sys/bus/usb/drivers_autoprobe to 0!

The team should consider rewording their installation guide.