moby--moby/docs/man/docker-build.1.md

% DOCKER(1) Docker User Manuals % William Henry % APRIL 2014

NAME

docker-build - Build an image from a Dockerfile source at PATH

SYNOPSIS

docker build [--no-cache[=false]] [-q|--quiet[=false]] [--rm] [-t|--tag=TAG] PATH | URL | -

DESCRIPTION

This will read the Dockerfile from the directory specified in PATH. It also sends any other files and directories found in the current directory to the Docker daemon. The contents of this directory would be used by ADD commands found within the Dockerfile.

Warning, this will send a lot of data to the Docker daemon depending on the contents of the current directory. The build is run by the Docker daemon, not by the CLI, so the whole context must be transferred to the daemon. The Docker CLI reports "Sending build context to Docker daemon" when the context is sent to the daemon.

When a single Dockerfile is given as the URL, then no context is set. When a Git repository is set as the URL, the repository is used as context.

OPTIONS

-q, --quiet=true|false When set to true, suppress verbose build output. Default is false.

--rm=true|false When true, remove intermediate containers that are created during the build process. The default is true.

-t, --tag=tag The name to be applied to the resulting image on successful completion of the build. tag in this context means the entire image name including the optional TAG after the ':'.

--no-cache=true|false When set to true, do not use a cache when building the image. The default is false.

EXAMPLES

Building an image using a Dockefile located inside the current directory

Docker images can be built using the build command and a Dockerfile:

docker build .

During the build process Docker creates intermediate images. In order to keep them, you must explicitly set --rm=false.

docker build --rm=false .

A good practice is to make a sub-directory with a related name and create the Dockerfile in that directory. For example, a directory called mongo may contain a Dockerfile to create a Docker MongoDB image. Likewise, another directory called httpd may be used to store Dockerfiles for Apache web server images.

It is also a good practice to add the files required for the image to the sub-directory. These files will then be specified with the ADD instruction in the Dockerfile. Note: If you include a tar file (a good practice!), then Docker will automatically extract the contents of the tar file specified within the ADD instruction into the specified target.

Building an image and naming that image

A good practice is to give a name to the image you are building. There are no hard rules here but it is best to give the names consideration.

The -t/--tag flag is used to rename an image. Here are some examples:

Though it is not a good practice, image names can be arbtrary:

docker build -t myimage .

A better approach is to provide a fully qualified and meaningful repository, name, and tag (where the tag in this context means the qualifier after the ":"). In this example we build a JBoss image for the Fedora repository and give it the version 1.0:

docker build -t fedora/jboss:1.0

The next example is for the "whenry" user repository and uses Fedora and JBoss and gives it the version 2.1 :

docker build -t whenry/fedora-jboss:V2.1

If you do not provide a version tag then Docker will assign latest:

docker build -t whenry/fedora-jboss

When you list the images, the image above will have the tag latest.

So renaming an image is arbitrary but consideration should be given to a useful convention that makes sense for consumers and should also take into account Docker community conventions.

Building an image using a URL

This will clone the specified Github repository from the URL and use it as context. The Dockerfile at the root of the repository is used as Dockerfile. This only works if the Github repository is a dedicated repository.

docker build github.com/scollier/Fedora-Dockerfiles/tree/master/apache

Note: You can set an arbitrary Git repository via the git:// schema.

HISTORY

March 2014, Originally compiled by William Henry (whenry at redhat dot com) based on docker.io source material and internal work.