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remove references to obsolete versions, and rewrite stdin section 

This removes references to obsolete versions of Docker, and rewrites
the section on building from a Dockerfile piped through `stdin`.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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Sebastiaan van Stijn 2019-03-08 16:37:41 +01:00
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develop/develop-images/dockerfile_best-practices.md
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@ -101,38 +101,147 @@ Sending build context to Docker daemon 187.8MB
### Pipe Dockerfile through `stdin` ### Pipe Dockerfile through `stdin`
Docker 17.05 added the ability to build images by piping `Dockerfile` through Docker has the ability to build images by piping `Dockerfile` through `stdin`
`stdin` with a _local or remote build-context_. In earlier versions, building an with a _local or remote build context_. Piping a `Dockerfile` through `stdin`
image with a `Dockerfile` from `stdin` did not send the build-context. can be useful to perform one-off builds without writing a Dockerfile to disk,
or in situations where the `Dockerfile` is generated, and should not persist
afterwards.
**Docker 17.04 and lower** > The examples in this section use [here documents](http://tldp.org/LDP/abs/html/here-docs.html)
> for convenience, but any method to provide the `Dockerfile` on `stdin` can be
> used.
>
> For example, the following commands are equivalent:
>
> ```bash
> echo -e 'FROM busybox\nRUN echo "hello world"' | docker build -
> ```
>
> ```bash
> docker build -<<EOF
> FROM busybox
> RUN echo "hello world"
> EOF
> ```
>
> You can substitute the examples with your preferred approach, or the approach
> that best fits your use-case.
#### Build an image using a Dockerfile from stdin, without sending build context
Use this syntax to build an image using a `Dockerfile` from `stdin`, without
sending additional files as build context. The hyphen (`-`) takes the position
of the `PATH`, and instructs Docker to read the build context (which only
contains a `Dockerfile`) from `stdin` instead of a directory:
```bash
docker build [OPTIONS] -
``` ```
docker build -t foo -<<EOF
The following example builds an image using a `Dockerfile` that is passed through
`stdin`. No files are sent as build context to the daemon.
```bash
docker build -t myimage:latest -<<EOF
FROM busybox FROM busybox
RUN echo "hello world" RUN echo "hello world"
EOF EOF
``` ```
**Docker 17.05 and higher (local build-context)** Omitting the build context can be useful in situations where your `Dockerfile`
does not require files to be copied into the image, and improves the build-speed,
as no files are sent to the daemon.
If you want to improve the build-speed by excluding _some_ files from the build-
context, refer to [exclude with .dockerignore](#exclude-with-dockerignore).
> **Note**: Attempting to build a Dockerfile that uses `COPY` or `ADD` will fail
> if this syntax is used. The following example illustrates this:
>
> ```bash
> # create a directory to work in
> mkdir example
> cd example
>
> # create an example file
> touch somefile.txt
>
> docker build -t myimage:latest -<<EOF
> FROM busybox
> COPY somefile.txt .
> RUN cat /somefile.txt
> EOF
>
> # observe that the build fails
> ...
> Step 2/3 : COPY somefile.txt .
> COPY failed: stat /var/lib/docker/tmp/docker-builder249218248/somefile.txt: no such file or directory
> ```
#### Build from a local build context, using a Dockerfile from stdin
Use this syntax to build an image using files on your local filesystem, but using
a `Dockerfile` from `stdin`. The syntax uses the `-f` (or `--file`) option to
specify the `Dockerfile` to use, using a hyphen (`-`) as filename to instruct
Docker to read the `Dockerfile` from `stdin`:
```bash
docker build [OPTIONS] -f- PATH
``` ```
docker build -t foo . -f-<<EOF
The example below uses the current directory (`.`) as the build context, and builds
an image using a `Dockerfile` that is passed through `stdin` using a [here
document](http://tldp.org/LDP/abs/html/here-docs.html).
```bash
# create a directory to work in
mkdir example
cd example
# create an example file
touch somefile.txt
# build and image using the current directory as context, and a Dockerfile passed through stdin
docker build -t myimage:latest -f- . <<EOF
FROM busybox FROM busybox
RUN echo "hello world" COPY somefile.txt .
COPY . /my-copied-files RUN cat /somefile.txt
EOF EOF
``` ```
**Docker 17.05 and higher (remote build-context)** #### Build from a remote build context, using a Dockerfile from stdin
Use this syntax to build an image using files from a remote `git` repository,
using a `Dockerfile` from `stdin`. The syntax uses the `-f` (or `--file`) option to
specify the `Dockerfile` to use, using a hyphen (`-`) as filename to instruct
Docker to read the `Dockerfile` from `stdin`:
```bash
docker build [OPTIONS] -f- PATH
``` ```
docker build -t foo https://github.com/thajeztah/pgadmin4-docker.git -f-<<EOF
This syntax can be useful in situations where you want to build an image from a
repository does not contain a `Dockerfile`, or if you want to build with a custom
`Dockerfile`, without maintaining your own fork of the repository.
The example below builds an image using a `Dockerfile` from `stdin`, and adds
the `README.md` file from the ["hello-world" Git repository on GitHub](https://github.com/docker-library/hello-world).
```bash
docker build -t myimage:latest -f- https://github.com/docker-library/hello-world.git <<EOF
FROM busybox FROM busybox
COPY LICENSE config_distro.py /usr/local/lib/python2.7/site-packages/pgadmin4/ COPY README.md .
EOF EOF
``` ```
> **Under the hood**
>
> When building an image using a remote Git repository as build context, Docker
> performs a `git clone` of the repository on the local machine, and sends
> those files as build context to the daemon. This feature requires `git` to be
> installed on the host where you run the `docker build` command.
### Exclude with .dockerignore ### Exclude with .dockerignore
To exclude files not relevant to the build (without restructuring your source To exclude files not relevant to the build (without restructuring your source
@ -142,9 +251,9 @@ similar to `.gitignore` files. For information on creating one, see the
### Use multi-stage builds ### Use multi-stage builds
[Multi-stage builds](multistage-build.md) (in [Docker 17.05](/release-notes/docker-ce/#17050-ce-2017-05-04) or higher) [Multi-stage builds](multistage-build.md) allow you to drastically reduce the
allow you to drastically reduce the size of your final image, without struggling size of your final image, without struggling to reduce the number of intermediate
to reduce the number of intermediate layers and files. layers and files.
Because an image is built during the final stage of the build process, you can Because an image is built during the final stage of the build process, you can
minimize image layers by [leveraging build cache](#leverage-build-cache). minimize image layers by [leveraging build cache](#leverage-build-cache).
@ -220,14 +329,13 @@ In older versions of Docker, it was important that you minimized the number of
layers in your images to ensure they were performant. The following features layers in your images to ensure they were performant. The following features
were added to reduce this limitation: were added to reduce this limitation:
- In Docker 1.10 and higher, only the instructions `RUN`, `COPY`, `ADD` create - Only the instructions `RUN`, `COPY`, `ADD` create layers. Other instructions
layers. Other instructions create temporary intermediate images, and do not create temporary intermediate images, and do not increase the size of the build.
directly increase the size of the build.
- In Docker 17.05 and higher, you can do [multi-stage builds](multistage-build.md) - Where possible, use [multi-stage builds](multistage-build.md), and only copy
and only copy the artifacts you need into the final image. This allows you to the artifacts you need into the final image. This allows you to include tools
include tools and debug information in your intermediate build stages without and debug information in your intermediate build stages without increasing the
increasing the size of the final image. size of the final image.
### Sort multi-line arguments ### Sort multi-line arguments