DockerCLI/docs/reference/commandline/build.md

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title = "build"
description = "The build command description and usage"
keywords = ["build, docker, image"]
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# build

    Usage: docker build [OPTIONS] PATH | URL | -

    Build a new image from the source code at PATH

      --build-arg=[]                  Set build-time variables
      --cpu-shares                    CPU Shares (relative weight)
      --cgroup-parent=""              Optional parent cgroup for the container
      --cpu-period=0                  Limit the CPU CFS (Completely Fair Scheduler) period
      --cpu-quota=0                   Limit the CPU CFS (Completely Fair Scheduler) quota
      --cpuset-cpus=""                CPUs in which to allow execution, e.g. `0-3`, `0,1`
      --cpuset-mems=""                MEMs in which to allow execution, e.g. `0-3`, `0,1`
      --disable-content-trust=true    Skip image verification
      -f, --file=""                   Name of the Dockerfile (Default is 'PATH/Dockerfile')
      --force-rm=false                Always remove intermediate containers
      --help=false                    Print usage
      -m, --memory=""                 Memory limit for all build containers
      --memory-swap=""                Total memory (memory + swap), `-1` to disable swap
      --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      --pull=false                    Always attempt to pull a newer version of the image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
      --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*](../builder.md#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](../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.

> **Note:**
> Currently only the "run" phase of the build can be canceled until pull
> cancellation is implemented).

## 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`:

    $ 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

    $ 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

    $ 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.

### Build with -

    $ 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.

### Usage of .dockerignore

    $ 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)

    $ 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`

### Specify Dockerfile (-f)

    $ 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 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#setting-ulimits-in-a-container).

### 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:

    $ 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.

For detailed information on using `ARG` and `ENV` instructions, see the
[Dockerfile reference](../builder.md).