How to use the command 'cloud-init' (with examples)

Cloud-init is a command line tool used for managing cloud instance initialization. It allows users to configure and customize cloud instances during the boot process. This article will provide examples of various use cases of the ‘cloud-init’ command.

Use case 1: Display the status of the most recent cloud-init run

Code:

cloud-init status

Motivation: By using this command, users can check the current status of the most recent cloud-init run. It helps in ensuring that the initialization process has completed successfully before proceeding with further actions on the cloud instance.

Explanation:

• cloud-init is the main command used to manage cloud instance initialization.
• status is an argument provided to the cloud-init command, which indicates that we want to display the status of the last cloud-init run.

Example output:

status: done

Use case 2: Wait for cloud-init to finish running and then report status

Code:

cloud-init status --wait

Motivation: This use case is useful when we want to wait for the cloud-init process to finish before executing any subsequent commands. It ensures that we have the updated status of the initialization process.

Explanation:

• cloud-init is the main command used to manage cloud instance initialization.
• status is an argument provided to the cloud-init command, which indicates that we want to display the status of the last cloud-init run.
• --wait is an optional argument that tells the command to wait until the initialization process finishes before reporting the status.

Example output:

status: done

Use case 3: List available top-level metadata keys to query

Code:

cloud-init query --list-keys

Motivation: This use case allows users to retrieve a list of available top-level metadata keys that can be queried using the cloud-init command. It helps in understanding the available metadata that can be accessed during the initialization process.

Explanation:

• cloud-init is the main command used to manage cloud instance initialization.
• query is an argument provided to the cloud-init command, which indicates that we want to query the metadata.
• --list-keys is an optional argument that specifies that we want to list the available top-level metadata keys.

Example output:

keys:
  - instance-id
  - local-hostname
  - public-keys
  - user-data

Use case 4: Query cached instance metadata for data

Code:

cloud-init query dot_delimited_variable_path

Motivation: In this use case, users can query specific dot-delimited variable paths to retrieve cached instance metadata. It allows users to access specific metadata values required for further customization or configuration.

Explanation:

• cloud-init is the main command used to manage cloud instance initialization.
• query is an argument provided to the cloud-init command, which indicates that we want to query the metadata.
• dot_delimited_variable_path is the specific dot-delimited variable path that needs to be queried.

Example output:

value: example_value

Use case 5: Clean logs and artifacts to allow cloud-init to rerun

Code:

cloud-init clean

Motivation: Running cloud-init clean allows users to remove logs and artifacts from previous cloud-init runs. This is useful when users want to re-run the initialization process without any remnants of previous configurations.

Explanation:

• cloud-init is the main command used to manage cloud instance initialization.
• clean is an argument provided to the cloud-init command, which initiates the cleaning process.

Example output:

Cleaning up previous cloud-init artifacts...

Conclusion:

In this article, we explored different use cases of the ‘cloud-init’ command. We learned how to display the status of the most recent cloud-init run, wait for it to finish running, list available top-level metadata keys, query cached instance metadata, and clean logs and artifacts. Understanding these use cases allows users to effectively manage and customize cloud instances during the initialization process.