April 25, 2005

Booting many operating systems on one box

My main workstation PC has two physical IDE hard disks. Since one of them is about 60G (and I don’t have that many mp3s), I figured I may as well install a few different operating systems on it.

At present, that consists of Debian r3.0 (woody), Debian unstable (sid), FreeBSD 4.6, OpenBSD 3.2 and finally Debian GNU/Hurd. Phew.

Partitions

Below is the layout of partitions on the disks.

mira:~# fdisk -l /dev/hda /dev/hdb

Disk /dev/hda: 255 heads, 63 sectors, 1028 cylinders
Units = cylinders of 16065 * 512 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/hda1             1         1      8001   83  Linux
/dev/hda2           393      1028   5108670    5  Extended
/dev/hda3             2       262   2096482+  a5  FreeBSD
/dev/hda4           263       392   1044225   a6  OpenBSD
/dev/hda5           393       963   4586526   83  Linux
/dev/hda6           964      1028    522081   82  Linux swap

Partition table entries are not in disk order

Disk /dev/hdb: 255 heads, 63 sectors, 7476 cylinders
Units = cylinders of 16065 * 512 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/hdb1             1         4     32098+  83  Linux
/dev/hdb2             5      7476  60018840    5  Extended
/dev/hdb5             5       490   3903763+  83  Linux
/dev/hdb6           491       612    979933+  83  Linux
/dev/hdb7           613       734    979933+  83  Linux
/dev/hdb8          2006      7476  43945776   83  Linux

grub

This is the grub config I use to boot them all:

title           Debian Woody GNU/Linux
root            (hd1,4)
kernel          /boot/vmlinuz-2.4.18 root=/dev/hdb5 ro
savedefault

title           Debian Sid GNU/Linux
root            (hd0,4)
kernel          /boot/vmlinuz-2.4.17 root=/dev/hda5 ro
savedefault

title           FreeBSD 4.6
root            (hd0,a)
kernel          /boot/loader
savedefault

title           OpenBSD 3.2
root            (hd0,3)
makeactive
chainloader +1
savedefault

title           Debian GNU/Hurd
root            (hd1,5)
kernel          /boot/gnumach.gz root=hd1s6
module          /boot/serverboot.gz
savedefault

Although I wouldn’t dream of doing it unless forced at knife-point (or threatened with suspension of my beer allowance), you can also convince grub to boot windows–against its better judgement.

Installation

If I really had any clue, I would have made careful notes as this sytem came together, so I could reproduce exactly what I did. Sigh. Anyhow, it started off with just the smaller hard disk (/dev/hda) containing a single install of Debian. When I got the groovy new 60Ger and decided to go nuts, I installed Debian Woody on that, and allocated a decent chunk to my /home filesystem. I then proceeded to carve up the original disk for various BSDs and Hurds.

A reasonable amount of research in the web before I started convinced me that it would all end in disaster, and my four year old debian sid install that started life as potato would be toast… but what the eh, it’s all in the name of science. As it turned out, it was far less traumatic than I thought–my biggest heart ache was discovering the particular mysterious incantations that grub needed for each OS.

It’s probably important that the *BSDs live in primary partitions–this will somewhat limit your flexibility in having six thousand OSes on a single disk. Linux is not so particular, and hurd would probably happily live in that little mat of fluff that gathers in the cooling vents of your PC.

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