docker-image-pull (1) - Linux Man Pages
docker-image-pull: Pull an image or a repository from a registry
docker-image-pull - Pull an image or a repository from a registry
docker image pull [OPTIONS] NAME[:TAG|@DIGEST]
This command pulls down an image or a repository from a registry. If there is more than one image for a repository (e.g., fedora) then all images for that repository name can be pulled down including any tags (see the option -a or --all-tags).
If you do not specify a REGISTRY_HOST, the command uses Docker's public registry located at registry-1.docker.io by default.
Pull an image from Docker Hub
To download a particular image, or set of images (i.e., a repository), use docker image pull. If no tag is provided, Docker Engine uses the :latest tag as a default. This command pulls the debian:latest image:
$ docker image pull debian Using default tag: latest latest: Pulling from library/debian fdd5d7827f33: Pull complete a3ed95caeb02: Pull complete Digest: sha256:e7d38b3517548a1c71e41bffe9c8ae6d6d29546ce46bf62159837aad072c90aa Status: Downloaded newer image for debian:latest
Docker images can consist of multiple layers. In the example above, the image consists of two layers; fdd5d7827f33 and a3ed95caeb02.
Layers can be reused by images. For example, the debian:jessie image shares both layers with debian:latest. Pulling the debian:jessie image therefore only pulls its metadata, but not its layers, because all layers are already present locally:
$ docker image pull debian:jessie jessie: Pulling from library/debian fdd5d7827f33: Already exists a3ed95caeb02: Already exists Digest: sha256:a9c958be96d7d40df920e7041608f2f017af81800ca5ad23e327bc402626b58e Status: Downloaded newer image for debian:jessie
To see which images are present locally, use the docker-images(1) command:
$ docker images REPOSITORY TAG IMAGE ID CREATED SIZE debian jessie f50f9524513f 5 days ago 125.1 MB debian latest f50f9524513f 5 days ago 125.1 MB
Docker uses a content-addressable image store, and the image ID is a SHA256 digest covering the image's configuration and layers. In the example above, debian:jessie and debian:latest have the same image ID because they are actually the same image tagged with different names. Because they are the same image, their layers are stored only once and do not consume extra disk space.
For more information about images, layers, and the content-addressable store, refer to about storage drivers <https://docs.docker.com/storage/storagedriver/> in the online documentation.
Pull an image by digest (immutable identifier)
So far, you've pulled images by their name (and "tag"). Using names and tags is a convenient way to work with images. When using tags, you can docker image pull an image again to make sure you have the most up-to-date version of that image. For example, docker image pull ubuntu:14.04 pulls the latest version of the Ubuntu 14.04 image.
In some cases you don't want images to be updated to newer versions, but prefer to use a fixed version of an image. Docker enables you to pull an image by its digest. When pulling an image by digest, you specify exactly which version of an image to pull. Doing so, allows you to "pin" an image to that version, and guarantee that the image you're using is always the same.
To know the digest of an image, pull the image first. Let's pull the latest ubuntu:14.04 image from Docker Hub:
$ docker image pull ubuntu:14.04 14.04: Pulling from library/ubuntu 5a132a7e7af1: Pull complete fd2731e4c50c: Pull complete 28a2f68d1120: Pull complete a3ed95caeb02: Pull complete Digest: sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2 Status: Downloaded newer image for ubuntu:14.04
Docker prints the digest of the image after the pull has finished. In the example above, the digest of the image is:
Docker also prints the digest of an image when pushing to a registry. This may be useful if you want to pin to a version of the image you just pushed.
A digest takes the place of the tag when pulling an image, for example, to pull the above image by digest, run the following command:
$ docker image pull ubuntu [at] sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2 sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2: Pulling from library/ubuntu 5a132a7e7af1: Already exists fd2731e4c50c: Already exists 28a2f68d1120: Already exists a3ed95caeb02: Already exists Digest: sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2 Status: Downloaded newer image for ubuntu [at] sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2
Digest can also be used in the FROM of a Dockerfile, for example:
FROM ubuntu [at] sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2 LABEL org.opencontainers.image.authors="some maintainer <maintainer [at] example.com>"
Note: Using this feature "pins" an image to a specific version in time. Docker will therefore not pull updated versions of an image, which may include security updates. If you want to pull an updated image, you need to change the digest accordingly.
Pulling from a different registry
By default, docker image pull pulls images from Docker Hub. It is also possible to manually specify the path of a registry to pull from. For example, if you have set up a local registry, you can specify its path to pull from it. A registry path is similar to a URL, but does not contain a protocol specifier (https://).
The following command pulls the testing/test-image image from a local registry listening on port 5000 (myregistry.local:5000):
$ docker image pull myregistry.local:5000/testing/test-image
Registry credentials are managed by docker-login(1).
Docker uses the https:// protocol to communicate with a registry, unless the registry is allowed to be accessed over an insecure connection. Refer to the insecure registries <https://docs.docker.com/engine/reference/commandline/dockerd/#insecure-registries> section in the online documentation for more information.
Pull a repository with multiple images
By default, docker image pull pulls a single image from the registry. A repository can contain multiple images. To pull all images from a repository, provide the -a (or --all-tags) option when using docker image pull.
This command pulls all images from the fedora repository:
$ docker image pull --all-tags fedora Pulling repository fedora ad57ef8d78d7: Download complete 105182bb5e8b: Download complete 511136ea3c5a: Download complete 73bd853d2ea5: Download complete Status: Downloaded newer image for fedora
After the pull has completed use the docker images command to see the images that were pulled. The example below shows all the fedora images that are present locally:
$ docker images fedora REPOSITORY TAG IMAGE ID CREATED SIZE fedora rawhide ad57ef8d78d7 5 days ago 359.3 MB fedora 20 105182bb5e8b 5 days ago 372.7 MB fedora heisenbug 105182bb5e8b 5 days ago 372.7 MB fedora latest 105182bb5e8b 5 days ago 372.7 MB
Canceling a pull
Killing the docker image pull process, for example by pressing CTRL-c while it is running in a terminal, will terminate the pull operation.
$ docker image pull fedora Using default tag: latest latest: Pulling from library/fedora a3ed95caeb02: Pulling fs layer 236608c7b546: Pulling fs layer ^C
Note: Technically, the Engine terminates a pull operation when the connection between the Docker Engine daemon and the Docker Engine client initiating the pull is lost. If the connection with the Engine daemon is lost for other reasons than a manual interaction, the pull is also aborted.