github.com/vieux/docker@v0.6.3-0.20161004191708-e097c2a938c7/man/docker-pull.1.md

% DOCKER(1) Docker User Manuals
% Docker Community
% JUNE 2014
# NAME
docker-pull - Pull an image or a repository from a registry

# SYNOPSIS
**docker pull**
[**-a**|**--all-tags**]
[**--help**] 
NAME[:TAG] | [REGISTRY_HOST[:REGISTRY_PORT]/]NAME[:TAG]

# DESCRIPTION

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. 

# OPTIONS
**-a**, **--all-tags**=*true*|*false*
   Download all tagged images in the repository. The default is *false*.

**--help**
  Print usage statement

# EXAMPLES

### Pull an image from Docker Hub

To download a particular image, or set of images (i.e., a repository), use
`docker pull`. If no tag is provided, Docker Engine uses the `:latest` tag as a
default. This command pulls the `debian:latest` image:

    $ docker 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 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 [understand images, containers, and storage drivers](https://docs.docker.com/engine/userguide/storagedriver/imagesandcontainers/)
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 pull` an
image again to make sure you have the most up-to-date version of that image.
For example, `docker 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 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:

    sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2

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 pull ubuntu@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@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2

Digest can also be used in the `FROM` of a Dockerfile, for example:

    FROM ubuntu@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2
    MAINTAINER some maintainer <maintainer@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 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 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/daemon/#insecure-registries)
section in the online documentation for more information.


## Pull a repository with multiple images

By default, `docker 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 pull`.

This command pulls all images from the `fedora` repository:

    $ docker 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 pull` process, for example by pressing `CTRL-c` while it is
running in a terminal, will terminate the pull operation.

    $ docker 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.


# HISTORY
April 2014, Originally compiled by William Henry (whenry at redhat dot com)
based on docker.com source material and internal work.
June 2014, updated by Sven Dowideit <SvenDowideit@home.org.au>
August 2014, updated by Sven Dowideit <SvenDowideit@home.org.au>
April 2015, updated by John Willis <john.willis@docker.com>
April 2015, updated by Mary Anthony for v2 <mary@docker.com>
September 2015, updated by Sally O'Malley <somalley@redhat.com>