Arch Linux

drewrockshard

Member

Registered: 2009-01-12

Posts: 3

USB SATA Drive - Grub Issues

I'm noticing an issue after installation that I'm unable to resolve.  First off here's my configuration.  I have 3 SATA drives attached to my laptop.  Two of the three are internal to the laptop (my laptop has two drive holders).  The 3rd sata drive is in an enclosed external case - so it is powered and accessed via USB.

The installer see's my drive as /dev/sdc.  When installing GRUB, it uses the UUID partitions - I changed that to the actual device names to make things easier for now.  So, my /etc/fstab is pointing its "root=" device to /dev/sdc3 (where the root / FS is partitioned on).  So, here I have no issues.  The issue is the fact that I choose /dev/sdc as the device to install GRUB.  I select it, and it says it installed correctly.  I then reboot the system.

This is where the issue begins.  It gives me the Arch splash screen and I try to boot into the installation, and it is using (hd2,0) - which makes sense - sense that is the 3rd drive.  So my grub root line is as follows:

root    (hd2,0)

It tries to boot this, and it says:

Filesystem type unknown, partition type 0xb
Error 17: Cannot mount selected partition

So, I have no idea why this is doing this.  If I change the root line in grub to:

root    (hd0,0)

It works.  No idea why.  Any live cd I boot into, sees the USB drive as /dev/sdc, no matter what.  And to be technically correct, hd0,0 would be /dev/sda - which is my Windows 7 installation.  So I have no idea why it actually things that this has grub installed on it.

Need some ideas as to why this is doing this and  how to resolve it.

rockin turtle

Member

From: Montana, USA

Registered: 2009-10-22

Posts: 227

Re: USB SATA Drive - Grub Issues

I'm not certain as I am not a GRUB expert.  It could be that since you installed GRUB on /dev/sdc, GRUB thinks that /dev/sdc is (hd0,0).  Had you installed GRUB on your /dev/sda (I'm NOT recommending this as it would probably screw up your Windows setup), then your menu.lst file would need to reference your external usb drive as (hd2,0).

Understand that GRUB runs before udev in the boot process (udev is responsible for naming all the devices in /dev), and therefore doesn't know anything about /dev/sda, /dev/sdb or /dev/sdc etc.

I'm not sure that this behavior can be changed.

drewrockshard

Member

Registered: 2009-01-12

Posts: 3

Re: USB SATA Drive - Grub Issues

Hmmm. Actually it makes sense. What if I had installed on /dev/sdc1?  Or would that just make it (hd0,1). Overall, about the udev thing you referenced really makes sense.