Disposable Debian VMs with debvm

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

Create a new virtual machine:

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.

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:

The additional options after -- are passed to mmdebstrap. In this case we’re specifying http://10.0.3.1:3142/debian 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 10.0.3.1, the IP address of the lxcbr0 interface used by qemu, instead of 127.0.0.1: to make sure that the guest VM has access to it too.

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

Start the VM:

SSH into the guest:

Enjoy!