Working with Docker Images

1. Pulling Images

Command	Description	Example
docker pull	Download an image from a registry	`docker pull nginx`
docker pull <image>:<tag>	Download a specific image tag	`docker pull node:18-alpine`

Example: Pulling a specific image tag

docker pull python:3.11-slim

Note: If no tag is specified, latest is assumed by default.

2. Listing Images

Command	Description	Options	Example
docker images	List all images on the local system	`-a` (all), `--format`, `--filter`	`docker images`
docker image ls	Alias for `docker images`	Same as `docker images`	`docker image ls`
docker images --format	Format output using Go template	`--format` with Go template syntax	`docker images --format "table {{.ID}}\t{{.Repository}}\t{{.Tag}}"`
docker images --filter	Filter images by criteria	`--filter` with key=value pairs (e.g., `reference=nginx`)	`docker images --filter "reference=nginx"`

Note: By default, docker images shows only the latest image per repository and tag. Use -a to show all images including intermediate ones.

3. Searching Images

Command	Description	Example
docker search	Search Docker Hub for images	`docker search nginx`
--filter	Filter search results by criteria	`docker search --filter is-official=true nginx`
--limit	Limit number of results (max 100)	`docker search --limit 10 nginx`

Example: Search for official Nginx images

docker search --filter is-official=true nginx

Example: Limit search results to 5

docker search --limit 5 node

Note: Docker Hub is the default registry. For private registries, use docker search [registry]/[image].

4. Inspecting Images

Command	Description	Example
docker inspect	Get detailed low-level information about an image or container	`docker inspect nginx`
docker image inspect	Alias for `docker inspect` when used with images	`docker image inspect node:18`
docker history	Show the history of an image including layers and commands	`docker history alpine:latest`

Example: Inspecting an Image

docker inspect nginx

Returns a JSON object with:

Image configuration
Mounts and volumes
Environment variables
Exposed ports
Entrypoint and CMD

Example: Viewing Image History

docker history node:18

Shows:

Each layer's command
Size of each layer
Creation time

Note: The docker inspect command returns a large JSON object. Use tools like jq to filter fields if needed.

5. Viewing Image History

Command	Description	Options	Example
docker history	Shows the history of an image	`--no-trunc` - Show full command lengths `--format` - Format output using Go template	`docker history nginx:latest`

Note: The docker history command does not show the full command that was used to create each layer. It only shows the commands that were run during the build process.

6. Tagging Images

Tag Format	Description	Example
repository:tag	Standard format for tagging images	`nginx:1.21`
registry/repository:tag	With registry prefix (e.g., Docker Hub)	`docker.io/library/nginx:1.21`
repository:latest	Default tag when no tag is specified	`nginx:latest`

Example: Tagging an Image

docker tag nginx:latest my-nginx:production

Example: Pushing Tagged Image

docker push my-nginx:production

Note: Tags are mutable; re-tagging the same image ID will update the tag reference.

7. Removing Images

Action	Command	Description
Remove image by ID or tag	`docker rmi [image-id\|image-name]`	Deletes the specified image from local storage
Force remove image	`docker rmi -f [image-id\|image-name]`	Removes image even if it is in use by a container
Remove image and all unused parents	`docker rmi --no-prune [image-id\|image-name]`	Removes image and any parent images that are not referenced by other images

Example: Remove a Docker Image

docker rmi nginx:latest

Note: If the image is currently being used by a running container, Docker will prevent removal unless you use docker rmi -f.

Warning: Removing an image will delete all layers associated with it, freeing up disk space. Be cautious when removing base images that may be used by other containers or images.

8. Pruning Unused Images

Example: Remove unused images

docker image prune

Option	Values	Notes
-a	`true`	Remove all unused images, not just dangling ones
--filter	`label=<key>=<value>`	Filter images by label
--force	`true`	Do not prompt for confirmation

Note: Dangling images are those with no tag and no containers using them.

Example: Remove images with specific label

docker image prune --filter label=environment=staging

Example: Remove all unused images without confirmation

docker image prune -a --force

9. Saving Images to Archive

Command	Description	Options	Example
docker save	Saves one or more images to a tar archive (streamed to STDOUT by default)	`--output, -o` to specify file output	`docker save -o my-image.tar nginx:latest`

Note: The archive includes all image layers and metadata, allowing for easy transport or backup.

Warning: Using docker save with multiple images requires specifying the -o option to avoid overwriting.

10. Loading Images from Archive

Action	Command	Description
Load image from tar archive	`docker load < image.tar`	Load a Docker image from a tar archive file
Load image with explicit file path	`docker load --input image.tar`	Load an image using the --input flag with file path
Load image and tag it	`docker load --input image.tar && docker tag old-name new-name`	Load image and apply a new tag to it after loading

Example: Loading a Docker Image Archive

# Save an image to a tar archive
docker save -o myapp.tar myapp:latest

# Load the image from the tar archive
docker load &lt; myapp.tar

Note: The docker load command reads the image from standard input or a file specified with --input. It can handle multiple images in one archive.

11. Filtering Images

Filter Type	Flag	Description	Example
Name	`--filter name=`	Filter by image name pattern	`docker images --filter name=nginx`
Reference	`--filter reference=`	Filter by image reference (tag or digest)	`docker images --filter reference=latest`
Label	`--filter label=`	Filter by label key=value	`docker images --filter label=version=1.0`
Before	`--filter before=`	Filter images created before a specific image ID or name	`docker images --filter before=nginx:latest`
Since	`--filter since=`	Filter images created after a specific image ID or name	`docker images --filter since=alpine:latest`
Dangling	`--filter dangling=true`	Filter dangling images (untagged images)	`docker images --filter dangling=true`

Example: Filtering by Label

docker images --filter label=environment=production

Example: Combining Filters

docker images --filter name=nginx --filter label=version=1.0

12. Displaying Image Digests

Command	Description	Example
docker images --digests	Lists all images with their digests	`docker images --digests`
docker inspect <image> --format '{{.Id}}'	Displays the image ID and digest	`docker inspect alpine:latest --format '{{.Id}}'`
docker image inspect <image>	Inspects image details including digest	`docker image inspect nginx:latest`

Note: Image digests are unique identifiers for image layers and help ensure content integrity.