Why would anyone in their right mind want to convert a VM into an ISO?
Good question, the answer for Conor Fox (who was the inspiration for this post - thanks Conor!) was to distribute his customized TurnKey PostgreSQL image so others could use it.
Distributing an ISO as opposed to a VM image allows it to be installed on any virtualization platform, as well as on bare metal, with the added bonus of running live.
I suppose that's a good enough reason, so lets get to it.
Convert VM disk to raw image and mount it
First we need to get qemu-img, a tool bundled with qemu (KVM's virtualization backend) to convert the VM disk to a raw image, and TKLPatch, the TurnKey customization mechanism to package the ISO.
If you are not using a TurnKey installation, see the TKLPatch installation notes.
apt-get install qemu apt-get install tklpatch
I'll show how to convert a VMWare VMDK image into raw disk format. If you are using a different virtualization platform such as Virtualbox, see this post on converting a VDI to a raw image.
qemu-img convert -f vmdk turnkey-core.vmdk -O raw turnkey-core.raw
Next, mount the raw disk as a loopback device.
mkdir turnkey-core.mount mount -o loop turnkey-core.raw turnkey-core.mount
GOTCHA 1: If your VM has partitions, it's a little tricker. You'll need to setup the loop device, partition mappings and finally mount the rootfs partition. You will need kpartx to setup the mappings.
loopdev=$(losetup -s -f turnkey-core.raw) apt-get install kpartx kpartx -a $loopdev # p1 refers to the first partition (rootfs) mkdir turnkey-core.mount mount /dev/mapper/$(basename $loopdev)p1 turnkey-core.mount
Extract root filesystem and tweak for ISO configuration
Now, make a copy of the root filesystem and unmount the loopback.
mkdir turnkey-core.rootfs rsync -a -t -r -S -I turnkey-core.mount/ turnkey-core.rootfs umount -d turnkey-core.mount # If your VM had partitions (GOTCHA 1): kpartx -d $loopdev losetup -d $loopdev
Because the VM is an installed system as opposed to the ISO, the file system table needs to be updated.
cat>turnkey-core.rootfs/etc/fstab<<EOF aufs / aufs rw 0 0 tmpfs /tmp tmpfs nosuid,nodev 0 0 EOF
GOTCHA 2: If your VM uses a kernel optimized for virtualization (like the one included in the TurnKey VM builds), you need to replace it with a generic kernel, and also remove vmware-tools if installed.
tklpatch-chroot turnkey-core.rootfs
# inside the chroot
apt-get update
apt-get install linux-image-generic
dpkg --purge $(dpkg-query --showformat='${Package}\n' -W 'vmware-tools*')
dpkg --purge $(dpkg-query --showformat='${Package}\n' -W '*-virtual')
exit
Generate the ISO
Finally, prepare the cdroot and generate the ISO.
tklpatch-prepare-cdroot turnkey-core.rootfs/ tklpatch-geniso turnkey-core.cdroot/
Thats it!
Bonus: By default the ISO will boot automatically. If you want to include the TurnKey bootsplash and bootmenu, extract the cdroot from a TurnKey ISO and tell tklpatch-prepare-cdroot to use it as a template.
tklpatch-extractiso turnkey-core.iso tklpatch-prepare-cdroot turnkey-core.rootfs/ turnkey-core.cdroot/ tklpatch-geniso turnkey-core.cdroot/
Ever needed to package a VM as a distributable ISO? Post a comment!