Images

Container images are unchanging static files that hold executable code and operate in isolation. A container image assembles all the components needed to create a container on an operating system, and it comprises different image layers stacked on top of each other. Container images are immutable.

Search registries

Container images are primarily searched on registries.

podman search almalinux

It will show all images related to the name almalinux.

NAME                                   DESCRIPTION
docker.io/library/almalinux            The official build of AlmaLinux OS.
docker.io/almalinux/almalinux          DEPRECATION NOTICE: This image is deprecated...
docker.io/almalinux/9-base             AlmaLinux release 9.8 base container image
docker.io/almalinux/8-base             AlmaLinux release 8.10 base container image
...

Podman defaults to docker.io, so podman search returns it.

Which registry to use also can be specified as follows,

podman search quay.io/almalinux

Now it will show results aggregated from quay.io registry

NAME                                        DESCRIPTION
quay.io/prometheus/node-exporter            # Node exporter  [![Build Status](https://gi...
quay.io/almalinuxorg/almalinux
quay.io/almalinuxorg/almalinux-bootc
quay.io/containerdisks/almalinux            # Almalinux Containerdisk Images  <img src="...
...

Pull

The url from the podman search can be used to get the container image (to local storage) using podman pull.

podman pull quay.io/almalinuxorg/almalinux

Trying to pull quay.io/almalinuxorg/almalinux:latest...
Getting image source signatures
Copying blob 653c5d8d0d66 skipped: already exists
Copying config de2f7b8674 done   |
Writing manifest to image destination
de2f7b867468d83dcc57f1ed18177debebabb064a42134067cdc9a3a2cd36536

As you may see, since no tag’s specified it default to latest.

Search on disk

To search the images present locally, either podman images or podman image ls can be used as both returns the same results.

podman images

REPOSITORY                      TAG         IMAGE ID      CREATED       SIZE
quay.io/almalinuxorg/almalinux  latest      de2f7b867468  4 days ago    194 MB

This will show the images available locally along with,

which repo it came from
tag (latest as the default if no tag is mentioned. Mentioning the appropriate tag is recommended rather than using latest)
Image ID that we can use to create containers instead of needing to type the long repo url and its size.

Note that the created date doesn’t come from when we pull but from when the container image is built.

Delete

Image ID, the whole url, or the name of an image can be used to remove the specific image. The name is the rest part excluding the domain (such as quay.io) or localhost. Unless specified by the image ID, the tag is necessary or it will defaults to :latest just like podman pull. Here, it is recommended to either use the whole url with the tag or the image ID to avoid unecessary troubles.

A locally stored image can be deleted or removed via podman image rm.

podman images

REPOSITORY                     TAG         IMAGE ID      CREATED            SIZE
localhost/main                 latest      f91f69dbf9eb  7 days ago         1.76 GB
docker.io/almalinux/10-base    latest      4a26427a4423  3 months ago       599 MB

podman image rm f91f69dbf9eb

Untagged: localhost/main:latest
Deleted: f91f69dbf9ebfd3f78d55893fbb81e9546c1ff2ac25c50d632008b617c20447d

podman image rm 10-base

Untagged: docker.io/almalinux/10-base:latest
Deleted: 4a26427a4423e96fd6e3991e4ff6dfe7397510e159e9482635b4cc395c5ce750

We will learn more about images, how we build, and related things later.