Executable Images

Note: This is only expected to work with Docker for Mac.

An executable image is an image that you run as if it were an executable.

Consider an example executable called myexec that prints the content of a file passed as its first argument. For this to work as a container, the path to the file inside and outside the container must match.

There is nothing novel about this project--it just captures some frequently-used docker run arguments that are necessary for all of this to work.

Features Supported

• Relative paths (under any of the absolute paths below)
• ~ and $HOME-based paths
• /tmp-based paths
• Interactive apps like vi
• Piping to stdin and stdout

Features Not Supported

• $TMPDIR-based paths: Docker for Mac automatically configures File Sharing for /tmp but $TMPDIR looks like /var/folders/3y/d44gn_2x7vv8d9d67969f54c0000gn/T/ which is not configured in File Sharing; the workaround is to use /tmp instead of $TMPDIR; if you pass paths based on $TMPDIR, they will not work; instead, use /tmp; example: mktemp --tmpdir=/tmp.

Contents of This Project

In this project there is a helper script called img-exec. It is meant to capture commonly-needed arguments to docker run when running images as executables. You can call into it, as will be demonstrated below, or just copy-and-modify the docker run arguments to meet your needs.

The following files/directories are at the root of this project:

• examples: Discussed below.
• img-exec: Helper script mentioned above.
• LICENSE-MIT.txt: License.
• README.md: This file.

In the examples directory, there are subdirectories demonstrating different features:

• paths: Demonstrates passing file paths to the container.
• pipes: Demonstrates piping input into and out of the container.
• vi: Demonstrates an interactive application like vi (vim).

Each subdirectory of examples has the following files:

• Dockerfile: Used to build the Docker image for the example.
• run: Main script copied into the image (and used as docker run --entrypoint argument.
• *-example: The script that calls into the img-exec helper script.
• Makefile: Used to run build and run targets.
• img-exec: A symlink to the main copy of img-exec.
• Supporting files, if any.

To run an example, change to that directory and run make build run. You can look into the Makefiles run target to see how it works.

Related

• Executable Images - How to Dockerize Your Development Machine
• bcbcarl/docker-vim