RPi tries to boot from the wrong USB-drive

I have two RPi’s both running DietPi. Both of them have two USB drives plugged in. One is a SanDisk and runs DietPi, the other is a Samsung and is mainly for backup purposes.

One of them tries to boot from the ‘backup’-USB. The other RPi doesn’t have that problem. It’s a recent problem, it worked fine in the past. I’ve checked the cmdline.txt if the correct partuuid is used, both have the correct USB-drive in there.

I do not understand why one fails to booth with that 2nd USB-drive inserted.

Any ideas?

Hi,

I guess you mean the RootFS is located on your external USB device? Correct? Did you checked /etc/fstab if settings for RootFS are correct as well? Next to that, you could have a look to dmesg. Right at the beginning you should find something like this:

[    0.000000] Kernel command line: coherent_pool=1M 8250.nr_uarts=1 snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 snd_bcm2835.enable_headphones=1 bcm2708_fb.fbwidth=720 bcm2708_fb.fbheight=480 bcm2708_fb.fbdepth=16 bcm2708_fb.fbswap=1 vc_mem.mem_base=0x3f000000 vc_mem.mem_size=0x3f600000  console=tty1 root=PARTUUID=2fed7fee-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet net.ifnames=0

Does it display the correct root=PARTUUID??

Thanks for the https://one2step.net solution Joulinar. Will update the results soon.