Cloud-init

Automate the configuration of your cloud instances using cloud-init.

What is Cloud-init?

Cloud-init is an industry standard for cross-platform cloud instance initialization. It is supported on most Linux distributions and is used to perform early initialization of a cloud instance during boot time.

With cloud-init, you can automate many common tasks when deploying instances, such as:

Setting the hostname
Adding SSH keys
Creating users and groups
Installing packages
Running custom scripts
Mounting file systems
Configuring networking

Cloud-init on MegaTech

On MegaTech, you can provide cloud-init configuration when creating a new instance. This configuration will be applied when the instance first boots up.

All Linux images provided by MegaTech come with cloud-init pre-installed and configured to run at boot time.

Note: Cloud-init is primarily used with Linux instances. Windows instances on MegaTech use a different initialization mechanism.

Cloud-init Configuration Formats

Cloud-init supports several configuration formats:

Cloud Config (YAML)

The most common format is cloud config, which uses YAML syntax. Cloud config files must start with #cloud-config on the first line.

#cloud-config
hostname: my-instance
users:
  - name: myuser
    groups: sudo
    shell: /bin/bash
    sudo: ['ALL=(ALL) NOPASSWD:ALL']
    ssh-authorized-keys:
      - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQ...
package_update: true
packages:
  - git
  - docker.io
  - python3-pip
runcmd:
  - systemctl start docker
  - systemctl enable docker

Shell Scripts

You can also use shell scripts, which must start with #!/bin/sh or similar shebang.

#!/bin/bash
# Update system
apt-get update
apt-get upgrade -y

# Install packages
apt-get install -y nginx git python3-pip

# Configure nginx
systemctl start nginx
systemctl enable nginx

# Clone repository
git clone https://github.com/myuser/myproject.git /opt/myproject

Common Cloud-init Tasks

Creating Users

#cloud-config
users:
  - name: myuser
    groups: sudo
    shell: /bin/bash
    sudo: ['ALL=(ALL) NOPASSWD:ALL']
    ssh-authorized-keys:
      - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQ...

Installing Packages

#cloud-config
package_update: true
package_upgrade: true
packages:
  - nginx
  - docker.io
  - python3-pip
  - build-essential

Running Commands

#cloud-config
runcmd:
  - systemctl start docker
  - systemctl enable docker
  - docker pull nginx:latest
  - [ pip3, install, django, flask, requests ]

Writing Files

#cloud-config
write_files:
  - path: /etc/nginx/sites-available/default
    content: |
      server {
        listen 80 default_server;
        listen [::]:80 default_server;
        root /var/www/html;
        server_name _;
        location / {
          try_files $uri $uri/ =404;
        }
      }
  - path: /var/www/html/index.html
    content: |
      <!DOCTYPE html>
      <html>
      <head>
        <title>Welcome to my instance!</title>
      </head>
      <body>
        <h1>Instance initialized with cloud-init</h1>
      </body>
      </html>

Using cloud-init with MegaTech

When creating a new instance through the MegaTech dashboard:

Navigate to the instance creation page
Select your preferred Linux image
Scroll down to the "Advanced Options" section
Look for the "User Data" or "Cloud-init" field
Paste your cloud-init configuration
Complete the instance creation process as usual

When using the MegaTech API to create instances, you can include the cloud-init configuration in the user_data field of your request.

Debugging Cloud-init

If your cloud-init configuration doesn't seem to be working as expected, you can check the logs to troubleshoot:

Check cloud-init status

cloud-init status

View cloud-init logs

cat /var/log/cloud-init.log

View cloud-init output log

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

Common issues: YAML syntax errors are the most frequent problem with cloud-init configurations. Make sure your indentation is correct and that you're using the proper format for your configuration.

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