docker-to-linux - make bootable Linux disk image abusing Docker

! Support development of this project > patreon.com/iximiuz

There is no real goal behind this project. Just out of my curiosity what if:

• launch a base Linux container (debian, alpine, etc)
• pull in Linux kernel & init system (systemd, OpenRC, etc)
• dump container's filesystem to a disk image
• install bootloader (syslinux) to this image...

Then it should be probably possible to launch a real virtual machine with such an image!

Try it out:

# 1. Build the image.
#    Depending on your setup, you may need to preceed `make` with `sudo`.
make debian  # or ubuntu, or alpine

# 2. Run it! Use username `root` and password `root` to log in.
qemu-system-x86_64 -drive file=debian.img,index=0,media=disk,format=raw -m 4096
# 2. Alternate
qemu-system-x86_64 -hda debian.qcow2 -m 512

# 3. Clean up when you are done.
make clean

It works!

You can increase or decrease the size of the VM hard disk via the environment variable VM_DISK_SIZE_MB (1024 by default).
For example for a 3GB disk:

make debian VM_DISK_SIZE_MB=3072  # or ubuntu, or alpine

Check out Makefile for more details or read my article on iximiuz.com.

Features

• Real quick build a bootable Linux image with a single command!
• 3 target distributives: Ubuntu 20.04, Debian Bullseye, Alpine 3.13.5
• Build from macOS (including M1 chips) or Linux hosts

FAQ

• Q: I'm getting an error about "read-only filesystem". How can I make it writable?

  A: It's Linux default behaviour to mount the / filesystem as read-only. You can always remount it with mount -o remount,rw /.

• Q: How can I access network from the VM / How can I SSH into the VM?

  A: Networking is not configured at the moment. If you want to configure it yourself, search for TUN/TAP/bridge devices. Don't forget to open a PR if you come up with a working solution.

Release notes

2021-05-24

• Start using ext4 instead of ext3.

2021-05-07

• Fix - Ubuntu 20.04 stopped working because of the changed path to vmlinuz and initrd files.

2021-05-02

• Fix macOS support #10 (thanks to @xavigonzalvo for reporting and suggesting the fix)
  • move losetup call from Makefile to the builder container
  • explicitly select amd64 architecture in target distr Dockerfiles to support builds on ARM hosts (aka M1)
• Upgrade target distr versions
  • Ubuntu 18.04 -> 20.04
  • Debian Stretch -> Bullseye
  • Alpine 3.9.4 -> 3.13.5

2020-02-29

• Improve Alpine support #7 (creds @monperrus)

2019-08-02

• Fix loopback device lookup #3 (creds @christau)

2019-06-03

• Initial release

TODO

• add basic networking support
• support different image formats (e.g. VirtualBox VDI)
• support different target architectures (e.g. ARM)

Similar projects

...or tangential projects relying on the similar technique:

• firecracker-microvm/firecracker suggests a similar trick to build custom VM rootfs images.
• weaveworks/ignite actually uses the same technique to build Firecracker VM images.
• d2vm (Docker to Virtual Machine) a CLI tool (written in Go) to build virtual machine images from Docker images (inspired by the docker-to-linux project).