making boot from previous internal drive now external work

Matt Patterson matt at
Mon Oct 24 17:53:01 UTC 2005

You definitely posted as a reply to an unrelated question. This is a 
relatively easy problem to solve and there are people with much more 
expertise than me. Basically what you need to do is figure out what 
device your "caddy" ends up on. If it is a usb device my guess is 
/dev/sda(1..9). If it is a standard ata connection then it will probably 
be /dev/hd(a..d). You could boot a live cd to figure that out, or from 
windows determine where the device shows up. USB, its as I said before. 
If it is ata, then primary master -> /dev/hda, primary slave -> 
/dev/hdb, etc.

Then you need to get access to the disk itself, probably from a live cd 
and edt /boot/grub/menu.lst. Inside you will find references like this:

title           Ubuntu, kernel 2.6.10-5-k7-smp
root            (hd0,0)
kernel          /boot/vmlinuz-2.6.10-5-k7-smp root=/dev/hda1 ro quiet splash
initrd          /boot/initrd.img-2.6.10-5-k7-smp

You will notice there are two different root references, one is the root 
line, one is within the kernel line. The kernel line needs to be updated 
with the device name I just referenced. The root line uses the grub 
device name format, which I havent played with in about a year, so I 
can't tell you the exact answer, but it is pretty straight forward. I am 
pretty sure a quick google search, or someone else on this list can 
answer that.


Sean Miller wrote:

> Right, a bit of background.
> Until about 3 weeks ago I had a Toshiba Laptop and I had it on dual 
> boot with Windows XP and Hoary Hedgehog.
> Unfortunately the laptop expired and so what I did was remove the hard 
> drive, put it in a little "caddy" and it is now an external drive -- 
> all well and good! :-)
> I have now got a new laptop and left the drive connected last night 
> and this morning when I booted up the screen said "GRUB" and hung.
> I quickly realised that it was trying to boot from the external drive, 
> and that got me thinking. I would really like to try booting into the 
> external hoary from this new laptop. It would be a great solution to 
> my wife's reluctance to let me dual boot her new "toy" (I'm currently 
> running Warty in VMWare but that is not ideal).
> Now, I'm sure it must be quite easy to modify the boot record on the 
> external drive to go straight into Ubuntu (or via GRUB - not an 
> issue)... to my way of thinking there are two problems at present...
> a) The boot record on the external drive presumably instructs grub to 
> look for its config at a location which is currently the internal 
> drive in the new laptop. So that needs to change.
> b) The grub config on the external drive will presumably also refer to 
> physical locations that are inside the new laptop.
> So we presumably need to modify the boot record and modify the grub 
> config?
> Anybody here got any advice on doing this? Help would be much 
> appreciated.
> Sean

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