24 KiB
| title | description | keywords |
|---|---|---|
| build | The build command description and usage | build, docker, image |
build
Usage: docker build [OPTIONS] PATH | URL | -
Build an image from a Dockerfile
Options:
--add-host value Add a custom host-to-IP mapping (host:ip) (default [])
--build-arg value Set build-time variables (default [])
--cache-from value Images to consider as cache sources (default [])
--cgroup-parent string Optional parent cgroup for the container
--compress Compress the build context using gzip
--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
--iidfile string Write the image ID to the file
--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
--network string Set the networking mode for the RUN instructions during build
'bridge': use default Docker bridge
'none': no networking
'container:<name|id>': reuse another container's network stack
'host': use the Docker host network stack
'<network-name>|<network-id>': connect to a user-defined network
--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--pull Always attempt to pull a newer version of the image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)
--security-opt value Security Options (default [])
--shm-size bytes Size of /dev/shm
The format is `<number><unit>`. `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.
--squash Squash newly built layers into a single new layer (**Experimental Only**)
-t, --tag value Name and optionally a tag in the 'name:tag' format (default [])
--target string Set the target build stage to build.
--ulimit value Ulimit options (default [])
Description
The docker build command builds Docker images from a Dockerfile and a
"context". A build's context is the set of 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 a COPY
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 fetches the
repository and its submodules. The commit history is not preserved. A
repository is first pulled into a temporary directory on your local host. After
that succeeds, the directory is sent to the Docker daemon as the context.
Local copy gives you the ability to access private repositories using local
user credentials, VPN's, and so forth.
Note: If the
URLparameter contains a fragment the system will recursively clone the repository and its submodules using agit clone --recursivecommand.
Git URLs accept context configuration in their fragment section, separated by a
colon :. The first part represents the reference that Git will check out,
and can be either a branch, a tag, or a remote reference. 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#pull/42/head |
refs/pull/42/head |
/ |
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 |
Tarball contexts
If you pass an URL to a remote tarball, the URL itself is sent to the daemon:
$ 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:
$ docker build - < Dockerfile
With Powershell on Windows, you can run:
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.
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:
$ docker build -t fail .
Sending build context to Docker daemon 2.048 kB
Sending build context to Docker daemon
Step 1/3 : FROM busybox
---> 4986bf8c1536
Step 2/3 : 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:
Examples
Build with PATH
$ docker build .
Uploading context 10240 bytes
Step 1/3 : FROM busybox
Pulling repository busybox
---> e9aa60c60128MB/2.284 MB (100%) endpoint: https://cdn-registry-1.docker.io/v1/
Step 2/3 : 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 3/3 : 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.
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. You can
specify an arbitrary Git repository by using the git:// or git@ scheme.
$ docker build -f ctx/Dockerfile http://server/ctx.tar.gz
Downloading context: http://server/ctx.tar.gz [===================>] 240 B/240 B
Step 1/3 : FROM busybox
---> 8c2e06607696
Step 2/3 : ADD ctx/container.cfg /
---> e7829950cee3
Removing intermediate container b35224abf821
Step 3/3 : 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 refers 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 -
$ 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.
Use a .dockerignore file
$ docker build .
Uploading context 18.829 MB
Uploading context
Step 1/2 : FROM busybox
---> 769b9341d937
Step 2/2 : CMD echo Hello world
---> Using cache
---> 99cc1ad10469
Successfully built 99cc1ad10469
$ echo ".git" > .dockerignore
$ docker build .
Uploading context 6.76 MB
Uploading context
Step 1/2 : FROM busybox
---> 769b9341d937
Step 2/2 : 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
Tag an 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.
Read more about valid tags.
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:
$ docker build -t whenry/fedora-jboss:latest -t whenry/fedora-jboss:v2.1 .
Specify a Dockerfile (-f)
$ docker build -f Dockerfile.debug .
This will use a file called Dockerfile.debug for the build instructions
instead of Dockerfile.
$ curl example.com/remote/Dockerfile | docker build -f - .
The above command will use the current directory as the build context and read a Dockerfile from stdin.
$ 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.
Use a custom 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.
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.
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.
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.
Optional security options (--security-opt)
This flag is only supported on a daemon running on Windows, and only supports
the credentialspec option. The credentialspec must be in the format
file://spec.txt or registry://keyname.
Specify isolation technology for container (--isolation)
This option is useful in situations where you are running Docker containers on
Windows. The --isolation=<value> 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".
Add entries to container hosts file (--add-host)
You can add other hosts into a container's /etc/hosts file by using one or
more --add-host flags. This example adds a static address for a host named
docker:
$ docker build --add-host=docker:10.180.0.1 .
Specifying target build stage (--target)
When building a Dockerfile with multiple build stages, --target can be used to
specify an intermediate build stage by name as a final stage for the resulting
image. Commands after the target stage will be skipped.
FROM debian AS build-env
...
FROM alpine AS production-env
...
$ docker build -t mybuildimage --target build-env .
Squash an image's layers (--squash) (experimental)
Overview
Once the image is built, squash the new layers into a new image with a single
new layer. Squashing does not destroy any existing image, rather it creates a new
image with the content of the squashed layers. This effectively makes it look
like all Dockerfile commands were created with a single layer. The build
cache is preserved with this method.
The --squash option is an experimental feature, and should not be considered
stable.
Squashing layers can be beneficial if your Dockerfile produces multiple layers modifying the same files, for example, file that are created in one step, and removed in another step. For other use-cases, squashing images may actually have a negative impact on performance; when pulling an image consisting of multiple layers, layers can be pulled in parallel, and allows sharing layers between images (saving space).
For most use cases, multi-stage are a better alternative, as they give more fine-grained control over your build, and can take advantage of future optimizations in the builder. Refer to the use multi-stage builds section in the userguide for more information.
Known limitations
The --squash option has a number of known limitations:
- When squashing layers, the resulting image cannot take advantage of layer sharing with other images, and may use significantly more space. Sharing the base image is still supported.
- When using this option you may see significantly more space used due to storing two copies of the image, one for the build cache with all the cache layers in tact, and one for the squashed version.
- While squashing layers may produce smaller images, it may have a negative impact on performance, as a single layer takes longer to extract, and downloading a single layer cannot be paralellized.
- When attempting to squash an image that does not make changes to the
filesystem (for example, the Dockerfile only contains
ENVinstructions), the squash step will fail (see issue #33823
Prerequisites
The example on this page is using experimental mode in Docker 1.13.
Experimental mode can be enabled by using the --experimental flag when starting the Docker daemon or setting experimental: true in the daemon.json configuration file.
By default, experimental mode is disabled. To see the current configuration, use the docker version command.
Server:
Version: 1.13.1
API version: 1.26 (minimum version 1.12)
Go version: go1.7.5
Git commit: 092cba3
Built: Wed Feb 8 06:35:24 2017
OS/Arch: linux/amd64
Experimental: false
[...]
To enable experimental mode, users need to restart the docker daemon with the experimental flag enabled.
Enable Docker experimental
Experimental features are now included in the standard Docker binaries as of version 1.13.0. For enabling experimental features, you need to start the Docker daemon with --experimental flag. You can also enable the daemon flag via /etc/docker/daemon.json. e.g.
{
"experimental": true
}
Then make sure the experimental flag is enabled:
$ docker version -f '{{.Server.Experimental}}'
true
Build an image with --squash argument
The following is an example of docker build with --squash argument
FROM busybox
RUN echo hello > /hello
RUN echo world >> /hello
RUN touch remove_me /remove_me
ENV HELLO world
RUN rm /remove_me
An image named test is built with --squash argument.
$ docker build --squash -t test .
[...]
If everything is right, the history will look like this:
$ docker history test
IMAGE CREATED CREATED BY SIZE COMMENT
4e10cb5b4cac 3 seconds ago 12 B merge sha256:88a7b0112a41826885df0e7072698006ee8f621c6ab99fca7fe9151d7b599702 to sha256:47bcc53f74dc94b1920f0b34f6036096526296767650f223433fe65c35f149eb
<missing> 5 minutes ago /bin/sh -c rm /remove_me 0 B
<missing> 5 minutes ago /bin/sh -c #(nop) ENV HELLO=world 0 B
<missing> 5 minutes ago /bin/sh -c touch remove_me /remove_me 0 B
<missing> 5 minutes ago /bin/sh -c echo world >> /hello 0 B
<missing> 6 minutes ago /bin/sh -c echo hello > /hello 0 B
<missing> 7 weeks ago /bin/sh -c #(nop) CMD ["sh"] 0 B
<missing> 7 weeks ago /bin/sh -c #(nop) ADD file:47ca6e777c36a4cfff 1.113 MB
We could find that all layer's name is <missing>, and there is a new layer with COMMENT merge.
Test the image, check for /remove_me being gone, make sure hello\nworld is in /hello, make sure the HELLO envvar's value is world.