Master Docker Image Management: List, Tag, Push, Save, and Delete

This tutorial series, authorized by WangWang Knowledge Base, continues the Docker image basics. Previously we introduced that a Docker image is a read‑only template and that Docker pulls missing images from Docker Hub.

Exploring More Image Operations

1. List local images

# docker images

REPOSITORY   TAG         IMAGE ID      CREATED         VIRTUAL SIZE
centos       latest      ce20c473cd8a  2 weeks ago     172.3 MB

2. Search images in the default registry

# docker search redis

3. Pull an image to the local host

# docker pull redis

Download progress may be slow from overseas servers; only a few basic images are needed.

4. Add a tag to an image

Tagging gives the image an easy‑to‑understand name and can specify a target repository for later push.

Key information displayed by docker images includes:

REPOSITORY: repository info, e.g., docker.io/redis
TAG: version label, default is latest
IMAGE ID: unique identifier of the image

Two ways to uniquely identify an image:

1. REPOSITORY:TAG (e.g., docker.io/centos:6.6)
2. IMAGE ID (e.g., 12c9d795d85a)

5. Push a modified image to a repository

# docker push 192.168.1.200:5000/centos:6.6

6. Save or load an image

Save an image to a tar file: # docker save -o redis.tar redis Load an image from a tar file:

# docker load --input redis.tar
# docker load < redis.tar

Loading restores the image and its metadata, enabling quick transfer between hosts without a private registry.

7. Delete an image

Remove a local image with:

# docker rmi redis
Untagged: redis:latest
Deleted: c08dd1f8fad9ff2622a1b5d74650a8e494ee380b74030e21584fea05079c2818
...

Note: Before deleting an image, first remove any containers that depend on it using docker rm.

8. How Docker images work

Docker images are built from multiple layers combined by a UnionFS. This allows a read‑only layer to be merged with a writable layer, enabling incremental modifications without altering the original image. Docker’s AUFS implementation follows the same principle.