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Cloud-init automatically configures a VPS during its very first boot — creating users, installing packages, running scripts — without requiring you to log in and configure it manually. Most major VPS providers support it natively.

What Cloud-Init Solves

Instead of provisioning a VPS and then manually running through your setup checklist, cloud-init lets you define that entire process as a single configuration file, applied automatically the moment the VPS boots for the first time.

Providing Cloud-Init Data

Most VPS providers offer a "User Data" field during instance creation in their control panel or API — this is where you paste your cloud-init configuration.

Basic Cloud-Init Example

#cloud-config
users:
  - name: deploy
    groups: sudo
    shell: /bin/bash
    sudo: ['ALL=(ALL) NOPASSWD:ALL']
    ssh_authorized_keys:
      - ssh-ed25519 AAAA...your-public-key...

package_update: true
package_upgrade: true

packages:
  - nginx
  - ufw
  - fail2ban

runcmd:
  - ufw allow OpenSSH
  - ufw allow 'Nginx Full'
  - ufw --force enable
  - systemctl enable --now fail2ban
  - systemctl enable --now nginx

Understanding the Structure

Writing Configuration Files via Cloud-Init

write_files:
  - path: /etc/motd
    content: |
      Welcome to this server.
      Managed by cloud-init.
    owner: root:root
    permissions: '0644'

Disabling Password Authentication from the Start

#cloud-config
ssh_pwauth: false

Setting the Hostname

#cloud-config
hostname: web-server-1
fqdn: web-server-1.yourdomain.com

Combining with a More Complete Hardening Script

runcmd:
  - sed -i 's/#Port 22/Port 2222/' /etc/ssh/sshd_config
  - sed -i 's/PermitRootLogin yes/PermitRootLogin no/' /etc/ssh/sshd_config
  - systemctl restart ssh
  - ufw allow 2222/tcp
  - ufw --force enable

This effectively automates much of How to Harden a Fresh Linux VPS in 15 Minutes to run automatically at first boot, with zero manual steps.

Testing Cloud-Init Configuration

After the VPS boots, verify cloud-init actually ran successfully:

sudo cloud-init status

sudo cat /var/log/cloud-init-output.log

Reusing Cloud-Init Configs Across Multiple Servers

Store your cloud-init YAML files in version control, parameterizing anything server-specific (hostname, SSH keys) so the same base template can provision consistent servers repeatedly — a lightweight complement to, or starting point before adopting, full infrastructure-as-code tools like Terraform.

Common Errors

Cloud-init configuration has no effect — verify the exact syntax, especially YAML indentation (which is strict), and confirm the provider actually passed your data as cloud-init user-data rather than a different mechanism.

SSH key doesn't work after boot — verify no formatting issues in the pasted public key, and that it's the full single-line key, not accidentally wrapped across multiple lines.

Best Practices

• Test your cloud-init configuration on a throwaway VPS before using it for production provisioning
• Version control your cloud-init templates alongside other infrastructure code
• Combine with Terraform for a complete, reproducible provisioning + configuration pipeline

Continue Reading

• How to Harden a Fresh Linux VPS in 15 Minutes
• Infrastructure as Code Basics: Managing VPS Config with Terraform
• How to Version Control Your Server Configuration

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