Re: How to create qemu-bootable image using debootstrap?

[David Barrett <dbarrett@quinthar.com>]

Matej Kosik wrote:
> Previously, I had the same problem but I did not know how to deal with
> the partions (btw. I still have too figure out how did you got those
> numbers to be able to create smaller disks). The `parted' stuff you
> posted before was a missing piece of information. Here is a complete
> sequence of commands that
> - creates a harddisk image
> - install multiboot specification compliant kernel to it
> - install grub to the harddisk image

Aha, excellent -- with your grub commands I was able to complete my
script. (Though I'm still not sure where the stage1/2/e2fs_stage1 should
come from -- currently it just copies off the host, which isn't that
clean but works for now.) I've posted it on my blog and will keep
updating it here:

http://blog.quinthar.com/2008/07/building-1gb-bootable-qemu-image-using.html

As for the magic numbers in the script to make it work for 1GB, here's
how I came up with them for the "dd" command:

bs = blocksize = 1024
count = 1GB/bs = (1024*1024*1024)/1024 = 1048576

For the "parted" command, I got the numbers by installing with the
netinst ISO onto a 1GB raw file, and then doing "parted test.raw print".
  I don't know how the netinst installer came up with those numbers,
but I just copied them.  Regardless, it seems like you can pretty much
choose whatever you want; I'm sure there's a whole science behind it.
(Where the "1069" came from I have no idea, as there are only 1024 MB on
disk.)

For the "loop,offset=16384" that took some guesswork: "parted print"
spit out 16.4K as the start of the first partition, and I guessed that
it was just rounding off 16384 and it worked.

Regardless, here it is for those of you following along.  Thanks for all
your help!

-david

-------------------

echo "Creating 1GB file of zeros in $1.raw"
dd if=/dev/zero of=$1.raw bs=1024 count=1048576

echo "Formating $1.raw with ext2 filesystem"
/sbin/parted $1.raw mklabel msdos
/sbin/parted $1.raw mkpart primary ext2 0 954
/sbin/parted $1.raw mkpart extended 954 1069
/sbin/parted $1.raw mkpart logical linux-swap 954 1069
/sbin/parted $1.raw set 1 boot on
/sbin/parted $1.raw mkfs 1 ext2

echo "Mounting $1.raw on $1.mount"
mkdir -p $1.mount
sudo mount -o loop,offset=16384 -t ext2 $1.raw $1.mount

echo "Installing Etch into $1.mount"
sudo debootstrap --arch i386 etch $1.mount http://ftp.us.debian.org/debian

echo "Setting up host networking in $1.mount for apt"
sudo cp /etc/resolv.conf $1.mount/etc
sudo cp /etc/hosts $1.mount/etc

echo "Installing kernel into $1.mount"
sudo chroot $1.mount apt-get update
sudo chroot $1.mount apt-get -y install gnupg
sudo chroot $1.mount apt-get update
echo "do_symlinks = yes
relative_links = yes
do_bootloader = yes
do_bootfloppy = no
do_initrd = yes
link_in_boot = no" > /tmp/kernel-img.conf
sudo mv /tmp/kernel-img.conf $1.mount/etc
sudo chroot $1.mount apt-get -y install linux-image-2.6-686

echo "Manually installing grub into $1.mount"
sudo mkdir -p $1.mount/boot/grub
sudo cp /boot/grub/stage1 $1.mount/boot/grub
sudo cp /boot/grub/stage2 $1.mount/boot/grub
sudo cp /boot/grub/e2fs_stage1_5 $1.mount/boot/grub
echo "default 0
timeout 0
title Linux
root (hd0,0)
kernel /boot/vmlinuz-2.6.18-6-686 root=/dev/hda1 ro
initrd /boot/initrd.img-2.6.18-6-686" > /tmp/menu.lst
sudo mv /tmp/menu.lst $1.mount/boot/grub
sudo echo "device (hd0) $1.raw
root (hd0,0)
setup (hd0)
quit" > /tmp/grub.input
sudo grub --device-map=/dev/null < /tmp/grub.input

echo "Configuring qemu networking"
echo "auto lo
iface lo inet loopback
allow-hotplug eth0
iface eth0 inet dhcp
" > /tmp/interfaces
sudo mv /tmp/interfaces $1.mount/etc/network

echo "Starting sshd and granting $USER a root key"
sudo chroot $1.mount apt-get -y install ssh
sudo chroot $1.mount /etc/init.d/ssh stop
sudo mkdir -p $1.mount/root/.ssh
sudo cp ~/.ssh/id_rsa.pub $1.mount/root/.ssh/authorized_keys
sudo chmod -R 755 $1.mount/root/.ssh

echo "Dismounting $1.mount"
sudo umount $1.mount

echo "Done. To start, run:"
echo ""
echo " sudo qemu -kernel-kqemu -redir tcp:2222::22 $1.raw"
echo ""
echo "To SSH in, run:"
echo ""
echo " ssh -p 2222 root@localhost"
echo ""