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 initialisation.

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 launch in a cloud environment the user provides user data consiting on a script or cloud-init directives that contain instructions for configuring 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: results of cloud-init execution are logged inside the unit /var/log/loud-init.log or /var/log/cloud-init-output.log. Additionaly it is possible to inspect instance early configuration using the AWS Console access.
  • 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 scripts 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:

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Javier Ruiz Cloud and SaaS Expert

Javier Ruiz

IT Wonder Lab tutorials are based on the diverse experience of Javier Ruiz, who founded and bootstrapped a SaaS company in the energy sector. His company, later acquired by a NASDAQ traded company, managed over €2 billion per year of electricity for prominent energy producers across Europe and America. Javier has over 25 years of experience in building and managing IT companies, developing cloud infrastructure, leading cross-functional teams, and transitioning his own company from on-premises, consulting, and custom software development to a successful SaaS model that scaled globally.

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