Docker Managing images
Syntax[edit | edit source]
- docker images [OPTIONS] [REPOSITORY[:TAG]]
- docker inspect [OPTIONS] CONTAINER|IMAGE [CONTAINER|IMAGE...]
- docker pull [OPTIONS] NAME[:TAG|@DIGEST]
- docker rmi [OPTIONS] IMAGE [IMAGE...]
- docker tag [OPTIONS] IMAGE[:TAG] [REGISTRYHOST/][USERNAME/]NAME[:TAG]
Listing locally downloaded images[edit | edit source]
$ docker images REPOSITORY TAG IMAGE ID CREATED SIZE hello*world latest 693bce725149 6 days ago 967 B postgres 9.5 0f3af79d8673 10 weeks ago 265.7 MB postgres latest 0f3af79d8673 10 weeks ago 265.7 MB
Fetching an image from Docker Hub[edit | edit source]
Ordinarily, images are pulled automatically from Docker Hub. Docker will attempt to pull any image from Docker Hub that doesn't already exist on the Docker host. For example, using
docker run ubuntu when the
ubuntu image is not already on the Docker host will cause Docker to initiate a pull of the latest
ubuntu image. It is possible to pull an image separately by using
docker pull to manually fetch or update an image from Docker Hub.
docker pull ubuntu docker pull ubuntu:14.04
Additional options for pulling from a different image registry or pulling a specific version of an image exist. Indicating an alternate registry is done using the full image name and optional version. For example, the following command will attempt to pull the
ubuntu:14.04 image from the
docker pull registry.example.com/username/ubuntu:14.04
Referencing images[edit | edit source]
Docker commands which take the name of an image accept four different forms:
Note: You can only refer to an image by its digest if that image was originally pulled using that digest. To see the digest for an image (if one is available) run
docker images --digests.
Removing Images[edit | edit source]
docker rmi command is used to remove images:
docker rmi <image name>
The full image name must be used to remove an image. Unless the image has been tagged to remove the registry name, it needs to be specified. For example:
docker rmi registry.example.com/username/myAppImage:1.3.5
It is also possible to remove images by their ID instead:
docker rmi 693bce725149
As a convenience, it is possible to remove images by their image ID by specifying only the first few characters of the image ID, as long as the substring specified is unambiguous:
docker rmi 693
Note: Images can be removed even if there are existing containers that use that image; docker rmi simply "untags" the image.
If no containers are using an image it is garbage-collected. If a container uses an image, the image will be garbage-collected once all the containers using it are removed. For example:
$ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 5483657ee07b hello-world "/hello" Less than a second ago Exited (0) 2 seconds ago small_elion $ docker rmi hello-world Untagged: hello-world:latest $ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 5483657ee07b 693bce725149 "/hello" Less than a second ago Exited (0) 12 seconds ago small_elion
Remove All Images With No Started Containers
To remove all local images that have no started containers, you can provide a listing of the images as a parameter:
docker rmi $(docker images -qa)
Remove All Images
If you want to remove images regardless of whether or not they have a started container use the force flag (
docker rmi -f $(docker images -qa)
Remove Dangling Images
If an image is not tagged and not being used by any container, it is 'dangling' and may be removed like this:
docker images -q --no-trunc -f dangling=true | xargs -r docker rmi
Search the Docker Hub for images[edit | edit source]
docker search <term>
$ docker search nginx NAME DESCRIPTION STARS OFFICIAL AUTOMATED nginx Official build of Nginx. 3565 [OK] jwilder/nginx*proxy Automated Nginx reverse proxy for docker c... 717 [OK] richarvey/nginx*php*fpm Container running Nginx + PHP-FPM capable ... 232 [OK] ...
Inspecting images[edit | edit source]
docker inspect <image>
The output is in JSON format. You can use
jq command line utility to parse and print only the desired keys.
docker inspect <image> | jq -r '..Author'
The above command will shows author name of the images.
Tagging images[edit | edit source]
Tagging an image is useful for keeping track of different image versions:
docker tag ubuntu:latest registry.example.com/username/ubuntu:latest
Another example of tagging:
docker tag myApp:1.4.2 myApp:latest docker tag myApp:1.4.2 registry.example.com/company/myApp:1.4.2
Saving and loading Docker images[edit | edit source]
docker save -o ubuntu.latest.tar ubuntu:latest
This command will save the
ubuntu:latest image as a tarball archive in the current directory with the name
ubuntu.latest.tar. This tarball archive can then be moved to another host, for example using
rsync, or archived in storage.
Once the tarball has been moved, the following command will create an image from the file:
docker load -i /tmp/ubuntu.latest.tar
Now it is possible to create containers from the
ubuntu:latest image as usual.