unixcommando
Posts: 18
Joined: Sun Dec 04, 2016 6:08 pm

Pi 4 hangs on boot with thumb drive connected

Sat Feb 22, 2020 11:43 am

I'm using a pi 4 to replace my pi 3B+ as my Octoprint server. To protect my gcode files I'm using 2 usb drives mirrored with mdadm to hold the code. When I boot the pi it hangs and I have to unplug the usb drives to boot it again, it hangs again when it tries to mount the mirror but plugging the usb drives back in allows it to mount the mirror and finish booting.

What might I be missing here? When I formated the drives I gave them a Linux partition label, so it shouldn't be trying to mount them as /boot.

epoch1970
Posts: 4469
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: Pi 4 hangs on boot with thumb drive connected

Sat Feb 22, 2020 5:28 pm

I would check cmdline.txt on the SD. root= might be pointing to the wrong device.
Or more precisely, might specify a non-unique target, so when the thumb drive is connected the machine tries erroneously to boot from it.
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

unixcommando
Posts: 18
Joined: Sun Dec 04, 2016 6:08 pm

Re: Pi 4 hangs on boot with thumb drive connected

Sun Feb 23, 2020 11:04 pm

You were very close. One of the SD cards had been used before with a Stretch image and had a partuuid the same as the boot SD card. I didn't see it because the filesystem UUID was unique so I was puzzled. Once I realized this was a different UUID I had to find a solution to change it. I had to install gdisk on my system to change this. It seems this should be easier to fix.

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