Installing grub on an HD image

[Eduardo Ochs]

Hi list,

Maybe I'm missing something basic, but how do I install grub
(preferably grub2) on an HD image that will later be used as an hd0 on
a Flash IDE adapter?

Here's what I'm trying to do (the real script is at
<http://angg.twu.net/e/plurall.e.html#loop-fdisk-mke2fs>):

--snip--snip--

# Create a zeroed HD image with 20MB
rm -v /tmp/test.img
dd if=/dev/zero of=/tmp/test.img bs=1M count=20

# Create two primary partitions: 1st=4M, 2nd=16MB
sudo fdisk -C 20 -H 64 -S 32 /tmp/test.img
n
p
1

4

n
p
2

20
u
p
w

# Some notes about how to get the offsets for "losetup -o",
# and the sizes of the partitions for mke2fs...
# (find-sh "echo -e 'u\\np\\nq' | sudo fdisk /tmp/test.img")
# 64 heads, 32 sectors/track, 0 cylinders, total 0 sectors
# Units = sectors of 1 * 512 = 512 bytes
#         Device Boot      Start         End      Blocks   Id  System
# /tmp/test.img1              32        8191        4080   83  Linux
# /tmp/test.img2            8192       40959       16384   83  Linux
# Sizes, in 512-byte blocks:
# (list "/tmp/test.img1" (+   -32  8191 1) (*  4080 2))
# (list "/tmp/test.img2" (+ -8192 40959 1) (* 16384 2))

# Associate the full image to a loop device
# (grub-setup may need this)
sudo losetup -f | tee             /tmp/test.dev0
sudo losetup                $(cat /tmp/test.dev0) /tmp/test.img

# Associate the first partition to a loop device,
# clear it, make an ext2 filesystem there, mount it.
sudo losetup -f | tee             /tmp/test.dev1
sudo losetup -o $[512*32]   $(cat /tmp/test.dev1) /tmp/test.img
sudo dd if=/dev/zero     of=$(cat /tmp/test.dev1) bs=1024 count=4080
sudo mke2fs -b 1024      -v $(cat /tmp/test.dev1)               4080
mkdir                                             /tmp/dev1
sudo mount -o loop          $(cat /tmp/test.dev1) /tmp/dev1

# Associate the second partition to a loop device,
# clear it, make an ext2 filesystem there, mount it.
sudo losetup -f | tee             /tmp/test.dev2
sudo losetup -o $[512*8192] $(cat /tmp/test.dev2) /tmp/test.img
sudo dd if=/dev/zero     of=$(cat /tmp/test.dev2) bs=1024 count=16384
sudo mke2fs -b 1024      -v $(cat /tmp/test.dev2)               16384
mkdir                                             /tmp/dev2
sudo mount -o loop          $(cat /tmp/test.dev2) /tmp/dev2

df

# Now copy the grub files to /tmp/dev1/boot/grub/
# and install grub on MBR of the HD image.
# (Omitted - my attempts to install grub on the image have failed!...)

# Umount, release loop devices
sudo umount                                       /tmp/dev1
sudo umount                                       /tmp/dev2
sudo losetup -d             $(cat /tmp/test.dev2) 2>&1 > /dev/null
sudo losetup -d             $(cat /tmp/test.dev1) 2>&1 > /dev/null
sudo losetup -d             $(cat /tmp/test.dev0) 2>&1 > /dev/null

--snip--snip--

By the way, after installing grub on the image the next steps are:

  * try to boot from that HD image with qemu,
  * make sure that grub recognizes the two partitions,
  * extract a linux kernel and an initrd from a certain liveCD
    (http://www.devil-linux.org/) and put them in the first partition,
  * enlarge the HD size to 256MB,
  * copy the CD image to the second partition (so that it cease to be
    ext2 and will become a compressed iso)
  * change the /linuxrc onthe initrd to make it start an interactive
    shell,
  * use that shell to mount (manually) the CD image from /dev/hda2
    instead of from a CD device, and then try to run pivotroot into it
    to run the liveCD,
  * change the CD detection functions in the /linuxrc script to make
    them handle a boot parameter like "cddevice=/dev/hda2".

If this works well then we will be able to run small liveCD images
(Devil Linux is ~ 200MB) on scrap machines that have no CD drive and
no HD, just by putting a 256MB flash IDE adapter on them...

  Cheers,
    Eduardo Ochs
    address@hidden
    http://angg.twu.net/