Docker build
External
Internal
Overview
docker build expects a Dockerfile and a context and uses the information provided to produce a Docker image.
docker build [options] <path>|<url>|-
The default location for the Dockerfile is the current directory, and the path is "."
The image such produced is placed in the local registry, using the repository name and the image tag provided with -t command line option. Note that if no -t option is use, the image will still be built, but it will be "dangling". For more details see -t command line option.
The Build Context
The build context is a set of file located in a path, or at an URL, which are specified in the build command line. The commands in the Dockerfile are relative to the context.
The URL may refer to Git repositories, pre-package TAR files and plain text files.
.dockerignore
Options
-t, --tag
Even if the option is named "tag", it actually specifies the target image repository URL, ignoring the registry host name - the image is always placed in the local registry. In one of its simplest variants, the URL can be just a tag, indeed. Most commonly, the URL contains the namespace and the repository name, or just the repository name. For more details about a repository URL, see: URL.
docker build -t novaordis/centos-loop:latest .
If no name/tag information is provided, there is no default: the image may be stored with no repository and no tag, just with an image ID. An "unnamed" images is called "dangling":
REPOSITORY TAG IMAGE ID CREATED SIZE <none> <none> 4cfda3233bb6 5 seconds ago 204MB
Alternatively, if the only Dockerfile instruction is FROM, or ..., the name and the tag will be inferred from the base image.
If the name/tag combination already exists in the repository, the image they designate will be "unnamed" (dangled) and the new image that has just been built replaces it.
--rm
--rm=true
Remove intermediate containers after a successful build (default true).