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I am trying to make a template for my Ubuntu VMs mostly by following Techno Tim's instructions here. I differ from Tim by wanting to also install qemu-guest-agent so I can get the IP of the vm without having to do it manually. I do this before importing the .img by using the command virt-customize -a focal-minimal-cloudimg-amd64.img --install qemu-guest-agent. But unfortunately this does me the favor of setting the machine-id, which I do not want in my template. Now, I could also run virt-customize -a focal-minimal-cloudimg-amd64.img --delete /etc/machine-id as well as in /var/lib/dbus/machine-id which does the trick and deletes it. But unfortunately during boot of any new VM from that, the system boots with many errors because machine-id is not there and for some reason /etc is mounted as read only. Is there any way to fix this?

I can get around this by instead of deleting with virt-customize, I can put in a firstboot script through virt-customize that deletes and regenerates a machine-id with a reboot to make it take effect, but this seems like a less than ideal way to do this. Is there a better way?

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Do not delete /etc/machine-id. Instead, truncate it with a command like truncate -s 0 /etc/machine-id /var/lib/dbus/machine-id. The machine-id file does not get created if it is deleted, but it will get populated with a new value if it is empty.

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Indeed /etc/machine-id must at least exist (empty is okay) in order to regenerate it -- then systemd will create a new one in a temporary location in /run, bind-mount /etc/machine-id to it, and systemd-machine-id-commit.service will then write it to /etc/machine-id once the fs becomes read-write

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    That did the trick, thanks so much! I used the command virt-customize -a focal-minimal-cloudimg-amd64.img --install qemu-guest-agent --truncate /etc/machine-id in case anyone else needs it. It seemsvirt-customize doesn't create /var/lib/dbus/machine-id because it said it didn't exist when i tried to delete it. Commented May 27, 2022 at 18:11
  • While facing an IP conflict between two VMs sharing the same cloud-init template, --truncate /etc/machine-id helped me a lot. To be sure the template is completely clean and stateless I also added --run-command 'cloud-init clean --logs'--run-command 'rm -rf /var/lib/cloud/'. Commented Jun 18 at 15:49

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