How to Use the Command 'podman images' (with examples)

Podman is a popular open-source tool used for managing container images and running containers without requiring a daemon process, which makes it a practical alternative to Docker for certain use cases. The ‘podman images’ command is a powerful utility within Podman that provides you with the capability to manage and list container images. This command allows you to perform various actions related to displaying and filtering information about images stored on your system.

Use case 1: List all Podman images

Code:

podman images

Motivation:
One of the most common uses of the podman images command is to get a quick overview of all the container images available on your system. Whether you are managing a large number of images for different projects or simply want to audit what’s stored locally, this command is essential. It helps in organizing and keeping track of all the images, ensuring that you can efficiently manage your container resources.

Explanation:
The command podman images when executed without any options, lists all container images that are locally available on your system. It displays detailed information such as the repository name, tag, image ID, size, and the time since the image was created. This information is crucial for management and operational purposes.

Example Output:

REPOSITORY          TAG         IMAGE ID      CREATED        SIZE
docker.io/library/nginx   latest      abcd1234     2 days ago    133MB
docker.io/library/alpine  latest      efgh5678     5 days ago    5MB

Use case 2: List all Podman images including intermediates

Code:

podman images --all

Motivation:
When building images, intermediate images are often created as a part of the build process. These intermediate images are typically layers of an image that help in caching and speeding up the build process. Listing all images, including these intermediates, can be useful to understand the complete state of your builds and for cleanup operations if you’re running low on disk space.

Explanation:
The --all option included in the command podman images --all causes Podman to display not just the final images resulting from builds, but also any intermediate layers that were used along the way. This provides a more comprehensive view of all image data present on the system, aiding both in debugging and in conducting thorough cleanups.

Example Output:

REPOSITORY          TAG         IMAGE ID      CREATED        SIZE
<none>              <none>      12345678      2 days ago    60MB
docker.io/library/nginx   latest      abcd1234     2 days ago    133MB
docker.io/library/alpine  latest      efgh5678     5 days ago    5MB

Use case 3: List the output in quiet mode (only numeric IDs)

Code:

podman images --quiet

Motivation:
In scenarios where you are writing scripts or need to pass image IDs to other commands or programs, you might prefer a cleaner and more concise output. The quiet mode delivers just the essential information—image IDs—enabling you to streamline processes or automate tasks that involve image management.

Explanation:
The --quiet option when added to podman images results in a trimmed-down output, where only the image IDs are displayed. This is particularly useful for script automation or when you only need the IDs for further processing, avoiding the clutter of additional image metadata.

Example Output:

abcd1234
efgh5678
12345678

Use case 4: List all Podman images not used by any container

Code:

podman images --filter dangling=true

Motivation:
Containers often depend on underlying images, but over time, you may accumulate images that are no longer in use. These are known as “dangling” images. Identifying and potentially removing these images is crucial for freeing up storage space and maintaining a tidy environment.

Explanation:
The --filter option with the parameter dangling=true in podman images --filter dangling=true helps isolate those images that are not being used by any containers and do not bear a tag. This is an effective way to find out which images are safe to remove to reclaim disk space.

Example Output:

REPOSITORY          TAG         IMAGE ID      CREATED        SIZE
<none>              <none>      12345678      2 days ago    60MB

Use case 5: List images that contain a substring in their name

Code:

podman images "*image|image*"

Motivation:
Often, managing a vast collection of images necessitates the ability to quickly locate an image with a specific characteristic in its name. This is particularly handy in development and testing environments where images are frequently updated or versioned.

Explanation:
By using the podman images command with a naming filter like podman images "*image|image*", the command filters out only those images whose names contain the specified substring. The asterisk wildcard characters (*) and the pipe symbol (|) allow you to match varied naming patterns, effectively narrowing down the list to your desired specification.

Example Output:

REPOSITORY          TAG         IMAGE ID      CREATED        SIZE
docker.io/library/myimage  latest      hijk3456     1 week ago   300MB

Conclusion:

The podman images command offers numerous options to efficiently manage and view container images. Whether you are simply listing all images, including intermediates, filtering out unused images, or searching for specific naming patterns, this command provides versatile functionality. This flexibility is essential for developers, system administrators, and IT professionals who need to maintain an organized and efficient container environment.