This post is mostly a post-it for myself

I use kvm with virt-manager to manage a couple of VMs to develop stuff and test ideas.

Most of the time I install a Debian stable or testing distribution in a small VM and take it from there.
There’s always a little customizing after that like installing vim/a MySQL server/etc.

As installing Debian is time-consuming and the setup of the machines is mostly the same I wanted to create a template to simply clone and be done.

Steps to reproduce:
* fire up VM
* install clean Debian (I chose web + ssh-server, no desktop)
* install additional software (I added: vim, mysql-server, libnss-mdns, uuid)
* apt-get clean
* ssh-copy-id your ssh keys if you want to
* remove all entries from /etc/udev/rules.d/70-persistent-net.rules
* if you don’t want your VMs to have persistent network interfaces at all, delete /lib/udev/rules.d/75-persistent-net-generator.rules, though it might come back on udev updates
* save this script as /root/rename-vm.sh and chmod +x it (Adjust keyword and name generation to your liking)

#!/bin/bash
set -e
set -u
keyword="template"
name="debian-${1:-$(uuid)}"
if [ -n "$(grep $keyword /etc/hostname)" ]; then
echo $name | tr " " "-" > /etc/hostname
reboot
fi


You should now be able to clone the machine, boot it, log in as root ./rename-vm.sh “new name”.

Assuming you have libnss-mdns installed and a proper networking setup for your VMs it should then be available as debian-new-name.local.

Make sure to update the template from time to time. You might need to remove the persistent-net rules again.

Caveats: All the clones have the same ssh host key and user passwords.

About that set -e/set -u stuff, I’ve come to put that at the top of all my shell scripts, see: Writing Robust Bash Shell Scripts