Disposable Debian VMs with debvm

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Some notes on using debvm, an amazing piece of software I’ve started using only recently.

Create a new virtual machine:

$ debvm-create

You now have a virtual machine with Debian Sid of your host native architecture (probably amd64). The image file is called rootfs.ext4. You’ve got 1G of disk space in the VM.

You can now just run the VM! You will be automatically logged is as root.

$ debvm-run

Experiment in the VM, run all the sort of tests you have in mind. For example, one thing I commonly do is verifying that things work in a clean environment, as opposed to "on my machine".

If anything goes wrong, or if you just want to repeat the test: shutdown the guest, remove rootfs.ext4, and start again with debvm-create.

Now, especially if you intend creating and recreating VMs multiple times, it helps to use a local apt mirror as a cache to avoid fetching all the required packages from the internet over and over again. Install apt-cacher-ng on your host machine and point debvm-create at it:

$ debvm-create --

The additional options after -- are passed to mmdebstrap. In this case we’re specifying as the URL of our local apt mirror. It is going to be used both for image creation and as the only entry in /etc/apt/sources.list on the guest. This is the reason for using, the IP address of the lxcbr0 interface used by qemu, instead of to make sure that the guest VM has access to it too.

For a slightly more advanced example, we now want to:

  • run a arm64 VM

  • have more disk space availably, say 2G

  • install additional packages (curl and locales)

  • allow SSH as root with the given public keys, in this example the authorized_keys installed on the host

  • start the VM in the background with no console output

$ debvm-create -a arm64 -o sid-arm64.ext4 -z 2G -k ~/.ssh/authorized_keys -- --include curl,locales

Start the VM:

$ debvm-run -i sid-arm64.ext4 -s 2222 -g -- -display none &

SSH into the guest:

$ ssh -o NoHostAuthenticationForLocalhost=yes -p 2222 root@