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How to configure cloud-init

cloud-init is the standard for automatic VM initialization: creating users, installing packages, writing files, running commands. In the Hikube console, the cloud-init script is entered in the Cloud-Init script (User Data) field.

Prerequisites​

  • A Hikube account and a project
  • A Linux image: the cloud-init field is not offered for Windows images
  • Basic knowledge of the YAML format

Steps​

1. Enter the script at creation​

  1. Open Infrastructure > VM Instances > Create an Instance and fill in the General, Configuration and Storage steps.
  2. At the Network step, Initialization & Access section, turn on the Cloud-Init script (User Data) switch.
  3. Enter your configuration in the text area. It must start with #cloud-config.
  4. Finish the wizard and click Create instance.

The keys entered in Authorized SSH keys are injected by the platform: there is no need to repeat them in the script for the default user.

2. Examples​

Additional user with sudo​

user-data.yaml
#cloud-config
users:
  - default
  - name: deployer
    sudo: ALL=(ALL) NOPASSWD:ALL
    groups: sudo
    shell: /bin/bash
    ssh_authorized_keys:
      - ssh-ed25519 AAAA... deployer@ci

The default entry keeps the image's default user (for example ubuntu).

Packages installed at boot​

user-data.yaml
#cloud-config
package_update: true
package_upgrade: true
packages:
  - htop
  - curl
  - git
  - docker.io

Commands at boot​

user-data.yaml
#cloud-config
runcmd:
  - mkdir -p /opt/app
  - echo "VM initialized on $(date)" > /opt/app/init.log
  - systemctl enable --now docker

Web server​

Also allow the HTTP (80) and HTTPS (443) ports at the Network step.

user-data.yaml
#cloud-config
packages:
  - nginx
write_files:
  - path: /var/www/html/index.html
    content: |
      <!DOCTYPE html>
      <html>
      <head><title>Hikube VM</title></head>
      <body><h1>VM up and running</h1></body>
      </html>
runcmd:
  - systemctl enable --now nginx

3. Change the script of an existing VM​

  1. Open the VM detail page and click Edit.
  2. In Advanced Configuration, edit Cloud-Init script (User Data).
  3. Click Save.

The new script is saved, without restarting the VM, but it is not replayed automatically: go to the next step.

4. Replay the script​

  1. On a VM with Running status, click Reload UserData, from the Actions section of the detail page or from the Actions menu of the list. The console shows UserData reloaded: restart the VM to apply it.
  2. The reload does not restart the VM: the script is replayed at the next boot. The Actions section of the detail page shows the Restart the VM to apply the UserData notice, with a Restart button: click it to apply the script right away.

At restart, cloud-init treats the VM as a new instance: it runs the whole script again (runcmd, write_files, packages…) and regenerates the SSH host keys. Your SSH client then reports a host key change; remove the old entry with ssh-keygen -R <public-ip>.

When you change the SSH Keys of a VM, the console offers this reload directly in the SSH keys changed dialog: Reload user-data or Don't reload user-data.

Effects of a reload

A reload followed by a restart makes the VM run the whole cloud-init script again. Write idempotent scripts (with no unwanted effect if run several times), especially for runcmd and write_files.

Verification​

Connect to the VM and check the cloud-init status:

cloud-init status

Expected result:

status: done

Check the log if there is a problem:

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

Validate the syntax of a script before submitting it (on a machine where cloud-init is installed):

cloud-init schema --config-file user-data.yaml

The saved script is visible at any time on the detail page, Advanced Configuration > Cloud-Init User Data section.

Further reading​