USB drive changes drive order, prevents boot

[charlweed]

The default Fedora (11 anyway) setup configures the root drive as a mapped logical volume. This is now causing me serious headaches.Here is the grub.conf in question:


title Fedora (2.6.30.10-105.2.4.fc11.i686.PAE)
root (hd0,0)
kernel /vmlinuz-2.6.30.10-105.2.4.fc11.i686.PAE ro root=/dev/mapper/vg_trixter-lv_root quiet
initrd /initrd-2.6.30.10-105.2.4.fc11.i686.PAE.img

The problem is that when I boot with a USB drive attached to a port, my system won't boot. It hangs right after the GRUB screen. This surprises me, because I thought that the volume/partition labels would insure the correct operation of the drive mapper, regardless of the drive order provided by the motherboard after POST.

It's a REALLY long story why I need the USB drive attached, but let's just say I do.

So, is there any way to setup the device mapper to find/configure the correct partitions? Or is there some other solution besides removing the USB drive?

Thanks!

[charlweed]

If I could identify the physical volume ( currently /dev/sdb2 ) by ID and use that for my logical volume /dev/mapper/vg_trixter-lv_root , I think that would be real progress.

I'm wading through the lvm man pages now it is not so helpful...

[Rubberman]

To avoid this sort of problem, it is recommeded that you label your drives, and use the LABEL=name identifier in /etc/fstab instead of device id (/dev/sda1, etc) or UUID=id constructs. That will eliminate most of this sort of trouble. Ie, label your boot partition as /bootN, your root partition as /, and your swap space as SWAP-N where N any number, etc.

[oz]

You can check the following wiki page for some information and instructions on how to go about doing what Rubberman has recommended above:

Persistent block device naming - ArchWiki

The article was written for Arch Linux, but it works with other distros as well.

I've used both, the by-label and by-uuid methods on my own system with great success.

[charlweed]

Thanks folks, I'm going to try UUID in grub.conf, but I fear I am defeated at the BIOS level. If the USB device is connected after POST, the USB is the first drive. If I could boot, I think it would always be /dev/sda

As it is, my system loads GRUB, shows the menu, but then hangs without running the kernel. Probably it fails to load the kernel at all, but there is no error message of any kind.


I labeled my root filesystem
"trixter_root"
and my logical volume root partion is
/dev/mapper/vg_trixter-lv_root


I ran

e2label /dev/mapper/vg_trixter-lv_root trixter_root

And edited /boot/grub/grub.conf to become

title Fedora (2.6.30.10-105.2.4.fc11.i686.PAE)
        root (hd0,0)
        kernel /vmlinuz-2.6.30.10-105.2.4.fc11.i686.PAE ro root=LABEL=trixter_root quiet
        initrd /initrd-2.6.30.10-105.2.4.fc11.i686.PAE.img

This does not work, and I think it's because the LVM itself is breaking, because it's physical volume gets re-ordered when the USB drive is connected at boot time.

So I'll edit grub.conf, and try root=UUID=bla-bla-bla
But what I REALLY want is some way to use lvm to specify the phyisical volume by UUID. I really expected that to be built into lvm, but I can't find it...

[charlweed]

I now think this is some nasty, wicked, EVIL interaction between my kernel
(2.6.30.10-105.2.4.fc11.i686.PAE) and my motherboard (P4C800-E). I've tried various USB BIOS settings, but nothing helps.

GRUB loads, and I have used the grub command line to verify that
root (hd0,0) works
and that grub can "find" /vmlinuz-2.6.30.10-105.2.4.fc11.i686.PAE and /initrd-2.6.30.10-105.2.4.fc11.i686.PAE.img

When I boot from grub, without quiet, the console shows the typical initial log messages before the "Welcome to Fedora" message, but then it hangs. The welcome never shows.
No errors, no nothing.

I've tried a few kernel arguments, nousb, debug, but this is not going anywhere.