# build ```markdown Usage: docker build [OPTIONS] PATH | URL | - Build an image from a Dockerfile Options: --build-arg value Set build-time variables (default []) --cgroup-parent string Optional parent cgroup for the container --cpu-period int Limit the CPU CFS (Completely Fair Scheduler) period --cpu-quota int Limit the CPU CFS (Completely Fair Scheduler) quota -c, --cpu-shares int CPU shares (relative weight) --cpuset-cpus string CPUs in which to allow execution (0-3, 0,1) --cpuset-mems string MEMs in which to allow execution (0-3, 0,1) --disable-content-trust Skip image verification (default true) -f, --file string Name of the Dockerfile (Default is 'PATH/Dockerfile') --force-rm Always remove intermediate containers --help Print usage --isolation string Container isolation technology --label value Set metadata for an image (default []) -m, --memory string Memory limit --memory-swap string Swap limit equal to memory plus swap: '-1' to enable unlimited swap --no-cache Do not use cache when building the image --pull Always attempt to pull a newer version of the image -q, --quiet Suppress the build output and print image ID on success --rm Remove intermediate containers after a successful build (default true) --shm-size string Size of /dev/shm, default value is 64MB. The format is ``. `number` must be greater than `0`. Unit is optional and can be `b` (bytes), `k` (kilobytes), `m` (megabytes), or `g` (gigabytes). If you omit the unit, the system uses bytes. -t, --tag value Name and optionally a tag in the 'name:tag' format (default []) --ulimit value Ulimit options (default []) ``` 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*](../builder.md#add) instruction to reference a file in the context. The `URL` parameter can refer to three kinds of resources: Git repositories, pre-packaged tarball contexts and plain text files. ### Git repositories When the `URL` parameter points to 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, VPN's, 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`: ```bash $ 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` ### Tarball contexts If you pass an URL to a remote tarball, the URL itself is sent to the daemon: 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`: ```bash $ docker build http://server/context.tar.gz The download operation will be performed on the host the Docker daemon is running on, which is not necessarily the same host from which the build command is being issued. The Docker daemon will fetch `context.tar.gz` and use it as the build context. Tarball contexts must be tar archives conforming to the standard `tar` UNIX format and can be compressed with any one of the 'xz', 'bzip2', 'gzip' or 'identity' (no compression) formats. ### Text files 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`: ```bash $ docker build - < Dockerfile ``` With Powershell on Windows, you can run: ```powershell Get-Content Dockerfile | docker build - ``` If you use `STDIN` or specify a `URL` pointing to a plain text file, 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 is interpreted as relative to the root of the context. 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](../builder.md#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. If the build initiated a pull which is still running at the time the build is cancelled, the pull is cancelled as well. ## Return code 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`: ```bash $ docker build -t fail . Sending build context to Docker daemon 2.048 kB Sending build context to Docker daemon Step 1 : FROM busybox ---> 4986bf8c1536 Step 2 : 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: [*Dockerfile Reference*](../builder.md). ## Examples ### Build with PATH ```bash $ 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 `tar`d 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*](../builder.md#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. ### Build with URL ```bash $ 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. You can specify an arbitrary Git repository by using the `git://` or `git@` scheme. ```bash $ docker build -f ctx/Dockerfile http://server/ctx.tar.gz Downloading context: http://server/ctx.tar.gz [===================>] 240 B/240 B Step 0 : FROM busybox ---> 8c2e06607696 Step 1 : ADD ctx/container.cfg / ---> e7829950cee3 Removing intermediate container b35224abf821 Step 2 : CMD /bin/ls ---> Running in fbc63d321d73 ---> 3286931702ad Removing intermediate container fbc63d321d73 Successfully built 377c409b35e4 ``` This sends the URL `http://server/ctx.tar.gz` to the Docker daemon, which downloads and extracts the referenced tarball. The `-f ctx/Dockerfile` parameter specifies a path inside `ctx.tar.gz` to the `Dockerfile` that is used to build the image. Any `ADD` commands in that `Dockerfile` that refer to local paths must be relative to the root of the contents inside `ctx.tar.gz`. In the example above, the tarball contains a directory `ctx/`, so the `ADD ctx/container.cfg /` operation works as expected. ### Build with - ```bash $ 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. ```bash $ docker build - < context.tar.gz ``` This will build an image for a compressed context read from `STDIN`. Supported formats are: bzip2, gzip and xz. ### Usage of .dockerignore ```bash $ docker build . Uploading context 18.829 MB Uploading context Step 1 : FROM busybox ---> 769b9341d937 Step 2 : CMD echo Hello world ---> Using cache ---> 99cc1ad10469 Successfully built 99cc1ad10469 $ echo ".git" > .dockerignore $ docker build . Uploading context 6.76 MB Uploading context Step 1 : FROM busybox ---> 769b9341d937 Step 2 : 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](../builder.md#dockerignore-file) ### Tag image (-t) ```bash $ 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`. [Read more about valid tags](tag.md). You can apply multiple tags to an image. For example, you can apply the `latest` tag to a newly built image and add another tag that references a specific version. For example, to tag an image both as `whenry/fedora-jboss:latest` and `whenry/fedora-jboss:v2.1`, use the following: ```bash $ docker build -t whenry/fedora-jboss:latest -t whenry/fedora-jboss:v2.1 . ``` ### Specify Dockerfile (-f) ```bash $ docker build -f Dockerfile.debug . ``` This will use a file called `Dockerfile.debug` for the build instructions instead of `Dockerfile`. ```bash $ 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. ```bash $ 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 build` will return a `no such file or directory` error 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 why > `ADD ../file` will not work. ### Optional parent cgroup (--cgroup-parent) 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](../run.md#specifying-custom-cgroups). ### Set ulimits in container (--ulimit) Using the `--ulimit` option with `docker build` will cause each build step's container to be started using those [`--ulimit` flag values](./run.md#set-ulimits-in-container-ulimit). ### Set build-time variables (--build-arg) You can use `ENV` instructions in a Dockerfile to define variable values. These values persist in the built image. However, often persistence is not what you want. Users want to specify variables differently depending on which host they build an image on. A good example is `http_proxy` or source versions for pulling intermediate files. The `ARG` instruction lets Dockerfile authors define values that users can set at build-time using the `--build-arg` flag: ```bash $ docker build --build-arg HTTP_PROXY=http://10.20.30.2:1234 . ``` This flag allows you to pass the build-time variables that are accessed like regular environment variables in the `RUN` instruction of the Dockerfile. Also, these values don't persist in the intermediate or final images like `ENV` values do. Using this flag will not alter the output you see when the `ARG` lines from the Dockerfile are echoed during the build process. For detailed information on using `ARG` and `ENV` instructions, see the [Dockerfile reference](../builder.md). ### Specify isolation technology for container (--isolation) This option is useful in situations where you are running Docker containers on Windows. The `--isolation=` option sets a container's isolation technology. On Linux, the only supported is the `default` option which uses Linux namespaces. On Microsoft Windows, you can specify these values: | Value | Description | |-----------|---------------------------------------------------------------------------------------------------------------------------------------------------------------| | `default` | Use the value specified by the Docker daemon's `--exec-opt` . If the `daemon` does not specify an isolation technology, Microsoft Windows uses `process` as its default value. | | `process` | Namespace isolation only. | | `hyperv` | Hyper-V hypervisor partition-based isolation. | Specifying the `--isolation` flag without a value is the same as setting `--isolation="default"`.