Cloud-Init, templates, and clones

Why this matters in production

Manually installing 30 VMs is not feasible. Cloud-Init + templates lets you provision VMs consistently at scale.

The pattern

flowchart LR
  A[Install base OS in VM] --> B[Customise: packages, config]
  B --> C[Install cloud-init guest]
  C --> D[Clean up & convert to template]
  D --> E[Template]
  E --> F[Clone for each instance]
  F --> G[Customise on first boot]

Step 1: Create a base VM

Install a base OS in a VM exactly as you would for a single instance. Apply your standard configuration: packages, users, security settings.

Step 2: Install the Cloud-Init guest

In the base VM:

apt update && apt install -y cloud-init qemu-guest-agent

dnf install -y cloud-init qemu-guest-agent

For Windows, install cloudbase-init.

Step 3: Clean up

Before converting to a template, remove machine-specific data:

cloud-init clean --logs --seed
rm -f /etc/ssh/ssh_host_*
rm -f /var/lib/dhcp/*
history -c && shutdown -h now

Step 4: Convert to a template

In the GUI: right-click the VM → “Convert to Template”. CLI:

qm template 9000

Step 5: Clone instances

GUI: right-click the template → Clone. CLI:

qm clone 9000 100 --name web-01 --full 1

qm clone 9000 101 --name web-02 --full 0

Step 6: Customise on first boot

Proxmox passes Cloud-Init configuration to the VM at boot:

qm set 101 --ciuser admin --cipassword <hash> --sshkeys /root/.ssh/id_rsa.pub --ipconfig0 ip=10.10.100.50/24,gw=10.10.100.1 --searchdomain lab.example.com --nameserver 10.10.10.1

qm cloudinit update 101 && qm start 101

Common Cloud-Init parameters:

Production considerations

Common mistakes

• Storing plaintext passwords in Cloud-Init configuration.
• Modifying a template after conversion (it’s locked).
• Deleting the base disk of a template with linked clones.
• Forgetting to install cloud-init in the base VM.

Key takeaways

• Templates + Cloud-Init is the production way to provision at scale.
• Use mkpasswd --method=SHA-512 for password hashes.
• Linked clones share storage with the template; full clones are independent.

Knowledge check