Cloud-init

Cloud-init is a multi-distribution package that handles the early initialization of cloud instances.

Cloud-init is the industry standard multi-distribution method for cross-platform cloud instance initialization.

It is commonly used in cloud computing environments to perform various tasks during the instance’s first boot:

• User Data: When a new instance is launched in a cloud environment, the user provides user data consisting of a script or cloud-init directives with the instructions to configure the instance.
• Instance Launch: AWS injects the user data into the instance metadata.
• Cloud-init Execution: During the first boot of the instance, cloud-init reads the user data and executes the specified actions and tasks, such as setting up SSH keys, installing packages, or configuring users.
• Configurations: cloud-init processes the user data using modules, each responsible for a specific aspect of configuration.
• DataSource: cloud-init relies on a DataSource to retrieve information about the instance and its environment. AWS provides a metadata service with details like instance ID, hostname, and user data.
• Output and Logs: the results of the cloud-init execution are logged in /var/log/cloud-init.log or /var/log/cloud-init-output.log. Additionally, the early configuration of the instance can be inspected with the console output in the AWS Console.
• Completion: Once cloud-init completes its tasks, the instance is ready for use with the configured settings.

Cloud-Init and SSH Public Keys #

During instance launch, Cloud-init appends the AWS stored Public Key to the instance authorized_keys file inside the ~/.ssh/ directory.

Official Cloud-Init documentation.

See tutorials using Cloud-Init:

• AWS with Terraform: The Essential Guide (10/21) – AWS Key Pairs