Usage: docker build [OPTIONS] PATH | URL | - Build a new image from the source code at PATH -f, --file="" Name of the Dockerfile (Default is 'PATH/Dockerfile') --force-rm=false Always remove intermediate containers --no-cache=false Do not use cache when building the image --pull=false Always attempt to pull a newer version of the image -q, --quiet=false Suppress the verbose output generated by the containers --rm=true Remove intermediate containers after a successful build -t, --tag="" Repository name (and optionally a tag) for the image -m, --memory="" Memory limit for all build containers --memory-swap="" Total memory (memory + swap), `-1` to disable swap -c, --cpu-shares CPU Shares (relative weight) --cpuset-mems="" MEMs in which to allow execution, e.g. `0-3`, `0,1` --cpuset-cpus="" CPUs in which to allow execution, e.g. `0-3`, `0,1` --cgroup-parent="" Optional parent cgroup for the container --ulimit=[] Ulimit options
Builds Docker images from a Dockerfile and a “context”. A build's context is the files located in the specified PATH or URL. The build process can refer to any of the files in the context. For example, your build can use an ADD instruction to reference a file in the context.
The URL parameter can specify the location of a Git repository; the repository acts as the build context. The system recursively clones the repository and its submodules using a git clone --depth 1 --recursive command. This command runs in a temporary directory on your local host. After the command succeeds, the directory is sent to the Docker daemon as the context. Local clones give you the ability to access private repositories using local user credentials, VPNs, and so forth.
Git URLs accept context configuration in their fragment section, separated by a colon :. The first part represents the reference that Git will check out, this can be either a branch, a tag, or a commit SHA. The second part represents a subdirectory inside the repository that will be used as a build context.
For example, run this command to use a directory called docker in the branch container:
$ docker build https://github.com/docker/rootfs.git#container:docker
The following table represents all the valid suffixes with their build contexts:
| Build Syntax Suffix | Commit Used | Build Context Used |
|---|---|---|
myrepo.git | refs/heads/master | / |
myrepo.git#mytag | refs/tags/mytag | / |
myrepo.git#mybranch | refs/heads/mybranch | / |
myrepo.git#abcdef | sha1 = abcdef | / |
myrepo.git#:myfolder | refs/heads/master | /myfolder |
myrepo.git#master:myfolder | refs/heads/master | /myfolder |
myrepo.git#mytag:myfolder | refs/tags/mytag | /myfolder |
myrepo.git#mybranch:myfolder | refs/heads/mybranch | /myfolder |
myrepo.git#abcdef:myfolder | sha1 = abcdef | /myfolder |
Instead of specifying a context, you can pass a single Dockerfile in the URL or pipe the file in via STDIN. To pipe a Dockerfile from STDIN:
docker build - < Dockerfile
If you use STDIN or specify a URL, the system places the contents into a file called Dockerfile, and any -f, --file option is ignored. In this scenario, there is no context.
By default the docker build command will look for a Dockerfile at the root of the build context. The -f, --file, option lets you specify the path to an alternative file to use instead. This is useful in cases where the same set of files are used for multiple builds. The path must be to a file within the build context. If a relative path is specified then it must to be relative to the current directory.
In most cases, it‘s best to put each Dockerfile in an empty directory. Then, add to that directory only the files needed for building the Dockerfile. To increase the build’s performance, you can exclude files and directories by adding a .dockerignore file to that directory as well. For information on creating one, see the .dockerignore file.
If the Docker client loses connection to the daemon, the build is canceled. This happens if you interrupt the Docker client with ctrl-c or if the Docker client is killed for any reason.
Note: Currently only the “run” phase of the build can be canceled until pull cancellation is implemented).
On a successful build, a return code of success 0 will be returned. When the build fails, a non-zero failure code will be returned.
There should be informational output of the reason for failure output to STDERR:
$ docker build -t fail . Sending build context to Docker daemon 2.048 kB Sending build context to Docker daemon Step 0 : FROM busybox ---> 4986bf8c1536 Step 1 : RUN exit 13 ---> Running in e26670ec7a0a INFO[0000] The command [/bin/sh -c exit 13] returned a non-zero code: 13 $ echo $? 1
See also:
$ docker build . Uploading context 10240 bytes Step 1 : FROM busybox Pulling repository busybox ---> e9aa60c60128MB/2.284 MB (100%) endpoint: https://cdn-registry-1.docker.io/v1/ Step 2 : RUN ls -lh / ---> Running in 9c9e81692ae9 total 24 drwxr-xr-x 2 root root 4.0K Mar 12 2013 bin drwxr-xr-x 5 root root 4.0K Oct 19 00:19 dev drwxr-xr-x 2 root root 4.0K Oct 19 00:19 etc drwxr-xr-x 2 root root 4.0K Nov 15 23:34 lib lrwxrwxrwx 1 root root 3 Mar 12 2013 lib64 -> lib dr-xr-xr-x 116 root root 0 Nov 15 23:34 proc lrwxrwxrwx 1 root root 3 Mar 12 2013 sbin -> bin dr-xr-xr-x 13 root root 0 Nov 15 23:34 sys drwxr-xr-x 2 root root 4.0K Mar 12 2013 tmp drwxr-xr-x 2 root root 4.0K Nov 15 23:34 usr ---> b35f4035db3f Step 3 : CMD echo Hello world ---> Running in 02071fceb21b ---> f52f38b7823e Successfully built f52f38b7823e Removing intermediate container 9c9e81692ae9 Removing intermediate container 02071fceb21b
This example specifies that the PATH is ., and so all the files in the local directory get tard and sent to the Docker daemon. The PATH specifies where to find the files for the “context” of the build on the Docker daemon. Remember that the daemon could be running on a remote machine and that no parsing of the Dockerfile happens at the client side (where you're running docker build). That means that all the files at PATH get sent, not just the ones listed to ADD in the Dockerfile.
The transfer of context from the local machine to the Docker daemon is what the docker client means when you see the “Sending build context” message.
If you wish to keep the intermediate containers after the build is complete, you must use --rm=false. This does not affect the build cache.
$ docker build . Uploading context 18.829 MB Uploading context Step 0 : FROM busybox ---> 769b9341d937 Step 1 : CMD echo Hello world ---> Using cache ---> 99cc1ad10469 Successfully built 99cc1ad10469 $ echo ".git" > .dockerignore $ docker build . Uploading context 6.76 MB Uploading context Step 0 : FROM busybox ---> 769b9341d937 Step 1 : CMD echo Hello world ---> Using cache ---> 99cc1ad10469 Successfully built 99cc1ad10469
This example shows the use of the .dockerignore file to exclude the .git directory from the context. Its effect can be seen in the changed size of the uploaded context. The builder reference contains detailed information on creating a .dockerignore file
$ docker build -t vieux/apache:2.0 .
This will build like the previous example, but it will then tag the resulting image. The repository name will be vieux/apache and the tag will be 2.0
$ docker build - < Dockerfile
This will read a Dockerfile from STDIN without context. Due to the lack of a context, no contents of any local directory will be sent to the Docker daemon. Since there is no context, a Dockerfile ADD only works if it refers to a remote URL.
$ docker build - < context.tar.gz
This will build an image for a compressed context read from STDIN. Supported formats are: bzip2, gzip and xz.
$ docker build github.com/creack/docker-firefox
This will clone the GitHub repository and use the cloned repository as context. The Dockerfile at the root of the repository is used as Dockerfile. Note that you can specify an arbitrary Git repository by using the git:// or git@ schema.
$ docker build -f Dockerfile.debug .
This will use a file called Dockerfile.debug for the build instructions instead of Dockerfile.
$ docker build -f dockerfiles/Dockerfile.debug -t myapp_debug . $ docker build -f dockerfiles/Dockerfile.prod -t myapp_prod .
The above commands will build the current build context (as specified by the .) twice, once using a debug version of a Dockerfile and once using a production version.
$ cd /home/me/myapp/some/dir/really/deep $ docker build -f /home/me/myapp/dockerfiles/debug /home/me/myapp $ docker build -f ../../../../dockerfiles/debug /home/me/myapp
These two docker build commands do the exact same thing. They both use the contents of the debug file instead of looking for a Dockerfile and will use /home/me/myapp as the root of the build context. Note that debug is in the directory structure of the build context, regardless of how you refer to it on the command line.
Note:
docker buildwill return ano such file or directoryerror if the file or directory does not exist in the uploaded context. This may happen if there is no context, or if you specify a file that is elsewhere on the Host system. The context is limited to the current directory (and its children) for security reasons, and to ensure repeatable builds on remote Docker hosts. This is also the reason whyADD ../filewill not work.
When docker build is run with the --cgroup-parent option the containers used in the build will be run with the corresponding docker run flag.
Using the --ulimit option with docker build will cause each build step's container to be started using those --ulimit flag values.