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Container to Virtual Machine (c2vm)

Create virtual machines from containers derived from Ubuntu LTS (18.04 or 20.04). Other OS may be supported later. This is a proof-of-concept: Create bootable VMs from existing container images. Docker is used for image building and execution. The process could be adapted to buildah and podman.

The build script buildVM.sh performs all operations within a builder container. It creates a bootable partition in a loop back device. Then it extends the provided image with a bootstrap image that install a kernel, systemd and some utils. The previously created partition is mounted and then the bootstrap image is exported there. extlinux is installed and an MBR is written.

The usage of extlinux and creation of filesystem via loop devices was inspired by https://github.com/iximiuz/docker-to-linux.git

Required software

docker installed on a Linux platform (WSL2 works) if you use the builder container. If you want to run the build script directly you need to have extlinux and qemu-utils installed.

Preparation

Create the builder image (c2vm/builder):

(cd builder && docker build -t c2vm/builder .)

Optional: Build the example images:

  • c2vm/examples/basic: Ubuntu 20.04 updated + git
  • c2vm/examples/devbox: Extends example and installs many development tools from (https://github.com/kaisalmen/wsltooling)
  • c2vm/examples/devboxui: Extends devbox and installs xfce4 and firefox
(cd examples/basic; docker build -t c2vm/examples/basic .)
(cd examples/devbox; docker build -t c2vm/examples/devbox .)
(cd examples/devboxui; docker build -t c2vm/examples/devboxui .)

Build VM image

Best use buildVM.sh from within c2vm/builder that was built before. Execute the script as specified below and change the two arguments as required:

  • 1: image to be converted and extended with bootstrap (e.g. c2vm/examples/basic)
  • 2: disk size MB (e.g. 2048, but for the larger images, you must create bigger initial partitions)
export LOOPDEV=$(losetup -f); \
docker run -it \
--env LOOPDEV=${LOOPDEV} \
-v /var/run/docker.sock:/var/run/docker.sock \
-v `pwd`:/workspace:rw \
--privileged \
--device ${LOOPDEV} \
c2vm/builder \
bash buildVM.sh c2vm/examples/basic 2048

Create a new VM with qemu/kvm, with Hyper-V or VirtualBox by using the virtuals disks linux.img, linux.vhdx or linux.vdi (conversion scripts are readily available).

Create a VM with KVM

Use the following command to quickly create a new VM from the disk image residing in staging or use virt-manager as UI to do it manually:

virt-install --import \
--disk ./staging/linux.img,cache=none \
--name=c2vm-kvm \
--vcpus=2 \
--memory=2048 \
--graphics spice \
--noautoconsole

Interacting with the VM and performing further configuration work is easiest via virt-manager.

Create a VM with Hyper-V

You need to have Windows 10, Hyper-V platform and administrative tools installed to be able to execute the following steps. Open a Powershell with administrative rights before you execute the following two commands.

New-VM -Name c2vm-hyperv -path .\staging\hyperv -MemoryStartupBytes 2GB -VHDPath .\staging\linux.vhdx
Start-VM -Name c2vm-hyperv

Extras

Transform container to WSL2:

Export the container:

docker export -o ./staging/devbox.tar $(docker run -d c2vm/examples/devbox /bin/true)

Copy to location where you can access the tarball with Powershell and import a new WSL

wsl --import devbox .\devbox devbox.tar --version 2

Utilities

Use dive for container inspection:

docker run --rm -it -v /var/run/docker.sock:/var/run/docker.sock wagoodman/dive:latest