Ubuntu 24.04 Proxmox Cloud-Init Prep

cloud-init Proxmox Ubuntu 24

Alt text

So yeah, templates are probably the least exciting thing to talk about, but I consider them foundational. Properly prepared templates mean less pain and simpler, more predictable deployments.

I keep cloud-init templates for just about every Linux distro an enterprise would care about. It gives me total freedom in how I deploy and makes it easy to compare behaviors across platforms.

This document provides a clean, repeatable, production grade procedure for building an Ubuntu 24.04 (Noble) template that works reliably with Proxmox cloud init.

Create an Ubuntu 24.04 VM template that reliably supports:

  • Static IP assignment via Proxmox
  • Root password injection
  • Root SSH authentication
  • Hostname injection
  • Clean, repeatable first‑boot behavior

Inside the Ubuntu VM (Before Templating)

Install Required Packages

apt update
apt install -y cloud-init qemu-guest-agent openssh-server

Enable services:

systemctl enable --now ssh
systemctl start qemu-guest-agent

Note: On Ubuntu 24.04, qemu-guest-agent may be a static unit. Starting it is sufficient.

Ensure Cloud-Init Is Enabled

ls /etc/cloud/cloud-init.disabled

If the file exists:

rm -f /etc/cloud/cloud-init.disabled

Force Proxmox Datasource (REQUIRED)

Ubuntu often ships with multiple datasources enabled. For Proxmox, force NoCloud.

cat > /etc/cloud/cloud.cfg.d/99-proxmox.cfg <<EOF
datasource_list: [ NoCloud, ConfigDrive ]
EOF

Verify:

cat /etc/cloud/cloud.cfg.d/99-proxmox.cfg

Allow Root SSH Login (IMPORTANT)

Ubuntu disables root login by default.

Set a root password:

passwd root
nano /etc/ssh/sshd_config

Ensure:

PermitRootLogin yes
PasswordAuthentication yes

Restart SSH:

systemctl restart ssh

Clean Cloud-Init State (NON‑OPTIONAL)

cloud-init clean --logs
truncate -s 0 /etc/machine-id
rm -f /var/lib/dbus/machine-id

Power off the VM:

shutdown -h now

Convert VM into a Cloud-Init Template (Proxmox Host)

Assuming VM ID is 124:

qm set 124 --ide2 local-lvm:cloudinit
qm set 124 --boot order=scsi0
qm template 124

The Ubuntu VM is now a reusable cloud-init template.

This is what it should look like from a Proxmox perspective in the UI

prox

Test Deployment (Clone + Configure + Boot)

This validates IP, hostname, root password, SSH, and metadata in one pass.

Clone the Template

qm clone 124 301 --name ubuntu-ci-test --full 1

Apply Cloud-Init Configuration (INCLUDING HOSTNAME)

qm set 401 \
  --ciuser root \
  --cipassword 'passwordhere' \
  --hostname vm-name-01 \
  --ipconfig0 ip=xxx.xx.x.xx/xx ,gw=xxx.xx.x.x \
  --nameserver xxx.xxx.xx.x\
  --searchdomain domain.com

Boot the VM

qm start 301

Validation Checklist

From another system:

ssh [email protected]

Inside the VM:

hostname
ip a
cloud-init status

Expected:

  • Hostname matches --hostname
  • Static IP applied correctly
  • cloud-init status: done
  • Root SSH login succeeds

If You See This Error

Use of uninitialized value in split at Cloudinit.pm line 115

It indicates stale or invalid cloud-init metadata.

Fix on Proxmox Host

qm set 301 --delete ciuser --delete cipassword --delete ipconfig0 --delete nameserver --delete searchdomain --delete hostname
qm set 301 --ide2 local-lvm:cloudinit

Then re-apply configuration and boot again.

That’s it. You should now have a repeatable way to deploy templates consistently. This same basic approach works with almost any operating system.

I keep multiple Linux flavors templated, so spinning up a fresh VM is trivial and predictable every time. Build once, reuse forever.

Hardening steps like disabling root SSH, enforcing key based authentication, and similar controls will be covered in later tutorials.

Thanks for reading!

-Christian

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