QEMU-utils

This is just another illustration for using tools in Singularity container.

Suppose, you want to upload an VM OS image to the cloud - in this example SNIC Science Cloud (SSC). Ubuntu provides them here and the format available is .img. For one or another reason (under heavy load compressed formats time out), you need to convert it to .raw with:

$ qemu-img convert -p -f qcow2 -O raw focal-server-cloudimg-amd64.img  focal-server-cloudimg-amd64.raw

Now, you can certainly do this on your computer, but you will end up with ~ 640MB .img to download and ~2GB .raw image that you need to upload. Depending on the Internet speed you have, this might be rather slow process.

If you have an account on UPPMAX and want to upload your image to the EAST region hosted by UPPMAX... yes, it is rather fast to do this operations remotely on Rackham. The problem is that qemu-tools are not available on Rackham...

Bootstrap: docker
From: ubuntu:latest

%environment
  export LC_ALL=C

%post
  export DEBIAN_FRONTEND=noninteractive
  export LC_ALL=C

  apt-get update && apt-get -y dist-upgrade && apt-get install -y git wget qemu-utils

%runscript
  /usr/bin/bash "$@"

Here is a bash script that will do everything...

#!/bin/bash
CMD_qemu_cmd="singularity exec /crex/proj/nobackup/sbin/qemu-utils.sif qemu-img"

TMP_DIR=$(mktemp -d) && \
cd ${TMP_DIR} && echo "TMP_DIR: "${TMP_DIR} && \
wget https://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img && \
${CMD_qemu_cmd} convert -p -f qcow2 -O raw focal-server-cloudimg-amd64.img  focal-server-cloudimg-amd64.raw && \
IMAGE_NAME=$(date -r focal-server-cloudimg-amd64.img +"Ubuntu 20.04 - %Y.%m.%d") && \
openstack image create --min-disk 20 --private --file focal-server-cloudimg-amd64.raw "${IMAGE_NAME}" && \
cd -

Note

You need to have the python-openstackclient to be able to run the command openstack image create ...