My machine has two hard drives -- /dev/sda and /dev/sdb. The first has Ubuntu installed. On the second, sdb, I want to install Gentoo. I did all the installation steps, chrooted and compiled the kernel, and installed lilo.

In lilo's configuration I have the following string:


/dev/sdb1 mounted as /boot. Lilo gives me a warning:

Warning: /dev/sdb is not on the first disk

When I try to boot I get:

unable to sync kernel panic. (Failed to find sdb3 on unknown device).

Is it any way related to the lilo warning? How do I fix it?

  • No, the panic message is not related to the lilo install warning. However unless you're removing the first disk when trying to boot off the second, installing lilo to the MBR of /dev/sdb shouldnt do anything as the BIOS will boot from the other disk first (unless you're changing BIOS boot order). It's been a long time since I've had to deal with "can't find root device" kernel panics, but IIRC, the kernel messages should show you what hard drives have been detected. If there aren't any, you may have left out support for your disk controller in the kernel config.
    – phemmer
    Commented Aug 14, 2012 at 23:15
  • Yes, I change boot order. Intresting. I get empty list of avaliable devices. Just got idea to copy ubuntu config. Will try.
    – KAction
    Commented Aug 15, 2012 at 4:11

1 Answer 1


This kernel panic means the kernel hasnt found the device that you told it to boot the system from. usually this happens when you forgot to compile the driver for the disk controller into the kernel, or you have it in initrd but forgot to load initrd.

if you used genkernel to build the kernel, its most likely the second problem. in that case please make sure you load the initrd correctly in your bootloader config.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .