dockerfile_best_practice.md

dockerfile best-practices

Pipe Dockerfile through stdin

Docker has the ability to build images by piping Dockerfile through stdin with a local or remote build context. Piping a Dockerfile through stdin 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.

echo -e 'FROM busybox\nRUN echo "hello world"' | docker build -

docker build -<<EOF
FROM busybox
RUN echo "hello world"
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.

docker build -t myimage:latest -<<EOF
FROM busybox
RUN echo "hello world"
EOF

Here’s an example from the buildpack-deps image:

RUN apt-get update && apt-get install -y \
  bzr \
  cvs \
  git \
  mercurial \
  subversion \
  && rm -rf /var/lib/apt/lists/*

Below is a well-formed RUN instruction that demonstrates all the apt-get recommendations.

RUN apt-get update && apt-get install -y \
    aufs-tools \
    automake \
    build-essential \
    curl \
    dpkg-sig \
    libcap-dev \
    libsqlite3-dev \
    mercurial \
    reprepro \
    ruby1.9.1 \
    ruby1.9.1-dev \
    s3cmd=1.1.* \
 && rm -rf /var/lib/apt/lists/*

Here is an example .dockerignore file:

# comment
*/temp*
*/*/temp*
temp?

This file causes the following build behavior:

Rule	Behavior
# comment	Ignored.
*/temp*	Exclude files and directories whose names start with temp in any immediate subdirectory of the root. For example, the plain file /somedir/temporary.txt is excluded, as is the directory /somedir/temp.

| | */*/temp* | Exclude files and directories starting with temp from any subdirectory that is two levels below the root. For example, /somedir/subdir/temporary.txt is excluded. | | temp? | Exclude files and directories in the root directory whose names are a one-character extension of temp. For example, /tempa and /tempb are excluded. |