How to Use the Command 'podman image' (with Examples)
Podman is a popular open-source containerization tool that offers users the ability to manage their container images, volumes, and other runtime features. Similar to Docker, Podman can be used to create, manage, and interact with containers and container images. The podman image command specifically focuses on managing Docker images. Whether you need to list, delete, or investigate the history of your Docker images, podman image has you covered. Below are some common use cases with detailed explanations of each command.
Use Case 1: List Local Docker Images
Code:
podman image ls
Motivation:
Listing local Docker images is essential for developers and system administrators to quickly ascertain which images are currently available on their local machines. This is especially useful for managing resources and determining which images need updates or can be removed. It’s a crucial step in maintaining an organized and efficient containerized environment.
Explanation:
podman: This is the base command to invoke Podman functionalities.image: This specifies that the operations to be performed are related to container images.ls: This stands for “list,” and it directs Podman to display all Docker images that are stored locally.
Example Output:
This command will output a table with image details such as repository, tag, image ID, creation date, and size:
REPOSITORY TAG IMAGE ID CREATED SIZE
alpine latest a0d0a0d0a0d0 2 months ago 5.61 MB
nginx stable b1b1b1b1b1b1 1 month ago 133 MB
Use Case 2: Delete Unused Local Docker Images
Code:
podman image prune
Motivation:
As developers work on building and running containers, unused images can accumulate over time, taking up valuable disk space. Pruning unused images helps clean up the system, freeing up storage resources. This is an essential maintenance task that ensures better performance and management of the container environment.
Explanation:
podman: This invokes the Podman tool.image: This specifies that the operation is image-related.prune: This argument directs Podman to remove all unused images, which typically means those not associated with a running or stopped container.
Example Output:
The command might display a summary of the reclaimed space:
Deleted Images:
sha256:c2c2c2c2c2c2
Total reclaimed space: 500 MB
Use Case 3: Delete All Unused Images
Code:
podman image prune --all
Motivation:
In some cases, users may need to go beyond removing simply unused images and want to delete all unused images, including those without a tag. This may be necessary if you want a complete clearing of unused images to recover disk space and start fresh.
Explanation:
podman: The command for using Podman functionalities.image: Indicates the operation pertains to Docker images.prune: Specifies that the unused images should be removed.--all: This flag specifies that all unused images should be deleted, including those without tags, offering a more thorough cleanup.
Example Output:
The command might denote images being removed and total space reclaimed, such as:
Deleted Images:
sha256:d3d3d3d3d3d3
sha256:e4e4e4e4e4e4
Total reclaimed space: 750 MB
Use Case 4: Show the History of a Local Docker Image
Code:
podman image history image
Motivation:
Understanding the history of a Docker image is crucial for developers who need insights into how an image was built. This includes information about each layer’s creation and modifications. Gathering these details is often essential for troubleshooting, security auditing, and optimizing image builds.
Explanation:
podman: Commands Podman to perform a task.image: Specifies that the task involves images.history: Requests the command to show the history or the sequence of layers and changes in an image.image: This should be replaced with the actual name or ID of the Docker image you want to investigate.
Example Output:
The command outputs details of each layer of the image history:
IMAGE CREATED CREATED BY SIZE
b1b1b1b1b1b1 1 month ago /bin/sh -c #(nop) CMD ["nginx" "-g" "daemon... 0B
b1b1b1b1b1b1 1 month ago /bin/sh -c #(nop) EXPOSE 80 0B
...
Conclusion:
The podman image command is an indispensable tool for managing Docker images efficiently. Whether listing images, removing unused ones, or digging into an image’s history, these commands facilitate a cleaner, more organized containerization workflow. Understanding and using these commands can greatly enhance the capability and maintainability of your systems, ensuring that your Docker images are handled with expertise and care.
