The Ubuntu version is 17.10 (Artful Aardvark), completely up to date. It was originally installed on a USB 3.0 key, was running on a x64 architecture system, and connected to an older (2.0) USB port. It was running perfectly fine.
Today I tried to boot the USB key on another system (same architecture, though). I've tried both 2.0 and 3.0 ports and got the same issues as I'll describe next.
Boot from BIOS seems fine, the GRUB menu and countdown are working, it starts booting with no issues, but at some point it stops, showing errors like:
- xhci_hcd 0000:00:10.0: Timeout waiting for setup device command
- usb 6-1: device not accepting address 2, error -62
- usb6-port1: unable to enumerate USB device
Eventually, it ends up reporting
gave up waiting for root device, with
Alert! UUID=<usb key uuid> does not exist. Dropping to a shell!!
At that point (on
initramfs console), if I just remove the USB key and plug it again, the USB key is recognized and then, after entering
exit in the console, Ubuntu starts normally.
Moreover, I tried the same on reboot, while getting the mentioned errors: just removed the USB key and plugged it back, and Ubuntu starts booting up (no initramfs this time).
So, it seems after moving the USB key to the new system, there something about USB ports that the original installation is not considering at boot time.
Update: I tried another approach, just to check if the USB version was an issue: I cloned the USB key 3.0 to a 2.0, and it worked perfectly on the new system.