Docker Images Cheat Sheet¶
What's a Docker Image?¶
A Docker image is a file used to execute code in a Docker container. Docker images act as a set of instructions to build a Docker container, like a template. Docker images also act as the starting point when using Docker. An image is comparable to a snapshot in virtual machine (VM) environments.
Images are just templates for docker containers.
docker imagesshows all images.
docker importcreates an image from a tarball.
docker buildcreates image from Dockerfile.
docker commitcreates image from a container, pausing it temporarily if it is running.
docker rmiremoves an image.
docker loadloads an image from a tar archive as STDIN, including images and tags (as of 0.7).
docker savesaves an image to a tar archive stream to STDOUT with all parent layers, tags & versions (as of 0.7).
While you can use the
docker rmi command to remove specific images, there's a tool called docker-gc that will safely clean up images that are no longer used by any containers. As of docker 1.13,
docker image prune is also available for removing unused images. See Prune.
Load an image from file:
docker load < my_image.tar.gz
Save an existing image:
docker save my_image:my_tag | gzip > my_image.tar.gz
Import a container as an image from file:
cat my_container.tar.gz | docker import - my_image:my_tag
Export an existing container:
docker export my_container | gzip > my_container.tar.gz
Difference between loading a saved image and importing an exported container as an image¶
Loading an image using the
load command creates a new image including its history.
Importing a container as an image using the
import command creates a new image excluding the history which results in a smaller image size compared to loading an image.
Thanks to @wsargent for creating this cheat sheet.