How to use the command 'docker secret' (with examples)

Docker secrets management is a critical feature for ensuring the safe storage and usage of confidential information within a Docker Swarm environment. Through the docker secret command, users can secure sensitive data such as passwords, API keys, and other credentials. These secrets can be programmatically consumed by Docker services within the swarm, ensuring that sensitive data is not exposed or hardcoded in application images.

Use case 1: Create a new secret from stdin

Code:

command | docker secret create secret_name -

Motivation:

Using Docker secrets from stdin is particularly useful when you want to create a secret dynamically, perhaps with data that isn’t already stored in a file. This allows for seamless integration in pipelines or scripts where secrets are generated on-the-fly. By using stdin, you minimize the necessity to store passwords or sensitive data on the filesystem, thus enhancing security measures.

Explanation:

• command: This represents any command that generates the secret data and outputs it to stdout.
• docker secret create: This is the command used to create a new secret in Docker Swarm.
• secret_name: The name assigned to the new secret. It should be a unique identifier for future reference.
• -: This hyphen signifies that the secret’s content is being read from stdin.

Example Output:

v7y9s1b4c3ex2q0fh29ir3o8x

The example output is a unique identifier returned by Docker when the secret is successfully created.

Use case 2: Create a new secret from a file

Code:

docker secret create secret_name path/to/file

Motivation:

This use case is ideal when your secret is already securely stored in a file. It streamlines the process by allowing you to directly create a Docker secret without manually entering the sensitive data. This is particularly useful in cases where secrets are part of a configuration management system or are generated automatically as files by other processes.

Explanation:

• docker secret create: Initiates the creation of a new secret.
• secret_name: A unique name for the secret, making it distinguishable within your swarm.
• path/to/file: The file path from where the secret’s content will be read. This file should contain the sensitive data intended to be stored as a secret.

Example Output:

0xg7s1b3f4ir2n9qh129c7e8a

The example output provides the secret’s unique identifier within the Swarm, confirming successful creation.

Use case 3: List all secrets

Code:

docker secret ls

Motivation:

Listing all secrets is crucial for managing and auditing current secrets within the Docker Swarm. It provides a quick overview of all the secrets, ensuring you can monitor existing secrets and identify any that may need to be updated or removed.

Explanation:

• docker secret ls: This command lists all the secrets available within the Docker Swarm. It doesn’t require any additional arguments and outputs a table with the identifiers and names of all secrets.

Example Output:

ID                          NAME                  CREATED             UPDATED
v7y9s1b4c3ex2q0fh29ir3o8x   database_password     2 days ago          2 days ago
0xg7s1b3f4ir2n9qh129c7e8a   api_key               5 hours ago         5 hours ago

The example shows a listing of secrets, with each entry’s ID, name, and timestamps.

Use case 4: Display detailed information on one or multiple secrets in a human-friendly format

Code:

docker secret inspect --pretty secret_name1 secret_name2 ...

Motivation:

Inspecting secrets in a human-friendly format is particularly useful in understanding not just the existence, but also the details such as creation and metadata attributes of secrets. This can be essential for debugging or when documenting your infrastructure’s security policies.

Explanation:

• docker secret inspect: This command is used to inspect one or more Docker secrets.
• --pretty: When added, it formats the output to be more readable for humans, rather than the raw JSON format.
• secret_name1 secret_name2 ...: The specific names of the secrets you want to inspect.

Example Output:

ID: v7y9s1b4c3ex2q0fh29ir3o8x
Name: database_password
Labels:
CreationTimestamp: 2023-10-01 14:45:30

ID: 0xg7s1b3f4ir2n9qh129c7e8a
Name: api_key
Labels:
CreationTimestamp: 2023-10-03 08:12:45

The detailed information includes the secret’s ID, name, labels, and when it was created.

Use case 5: Remove one or more secrets

Code:

docker secret rm secret_name1 secret_name2 ...

Motivation:

Managing secrets often involves updating and rotating them. Part of secure management includes removing secrets that are deprecated or no longer in use. This command helps maintain a clean state within your Docker Swarm, decreasing the risk of unauthorized access to outdated secrets.

Explanation:

• docker secret rm: Initiates the removal of one or more secrets from the Swarm.
• secret_name1 secret_name2 ...: The names of the secrets you wish to remove. Multiple secrets can be specified, separated by a space.

Example Output:

secret_name1
secret_name2

The output confirms the successful removal of each secret by reiterating the names of the removed items.

Conclusion

Through these use cases, the power and flexibility of the docker secret command are clearly illustrated. By efficiently managing secrets, Docker enhances the security posture of applications deploying within its ecosystem, allowing for a structured and secure way to handle sensitive data. These commands provide foundational yet essential tools for developers and IT administrators to safeguard their applications’ secrets.