View Full Version : [ubuntu] Dual boot grub explanation

September 4th, 2008, 08:59 PM
Hi guys I hve just dual booted using a guide on the net but am frustrated as I dont understand how I got it to work and really need to know as I can see simple solution to triple even quad boot in the future.

ok I have three hard disks.

so thats dev\sda, dev\sdb & dev\sdc

on sda I have ubuntu and on sdb I have two partitions and now vista just went on the second partition of disk 2 so thats dev\sdb2.

Ok the last part of the guide was to reinstate GRUB and add the new install as an option at the bottom.

i.e title VISTA
root (hd0,1)
chinloader +1

this was the default setting if you used the first disk.

Now remember I said VISTA is on the second disk second partition.
How come when I thought logically the root in grub needed to be HD1,2 in windows language disk 1 partition 2.

It didnt work, after guessing all combo's and nothing worked I ended using the exact same options in the example and it worked perfectly.

to me that option points to disk "0" partiton 1 which seems impossible as its on disk 2 partion 2. So really should be HD1,2.

Please help me understand so I can boot more linux distro's and also if I did would I just add another 4 lines pertaining to the new install. Thanks alot I can count on youbuntwo.:guitar:

Too Late
September 4th, 2008, 09:09 PM
In grub, both disk and partition numbers start from zero. Thus, sdb2 is (hd1,1). (Assuming that sda is the booting device.)

September 4th, 2008, 09:34 PM
cool thanks man but still dont get it

if that was the case then surely I should have successful boot from
edit (hd1,1) and not (hd0,1) as set currently

Too Late
September 5th, 2008, 08:00 AM
Ok, sorry, I didn't read your post very well. However, as I said in brackets, the device which is set bootable in BIOS (i.e. device which MBR has grub installed) will always be hd0. So probably your computer boots from sdb. I mean, the grub disk numbers (hd0, hd1...) depend on the booting order, so they don't necessarily correspond to linux device names (sda, sdb...). Furthermore, do you have PATA/IDE or SATA disks, or both? They would make things more complicated (at least now when PATA disks are also called sd*).

September 6th, 2008, 06:40 AM
arh right i see - well they are all sata so thats ok but i cant be 100% which bunts is booting off so it makes sense knowing that could be the issue - well not really an issue, just a bit of confusion on my part.

In the last 24 hours my GF hit a poisoned website on the xp laptop and it completely trashed it.

Putting dual boot skills into action so ubuntu for safer browsing and mail and a windows for word.

Thanks for clearing things up!!