baseimage-docker/README.md

A minimal Docker base image with a correct and usable system

Baseimage-docker is a Docker image meant to serve as a good base for any other Docker container. It contains a minimal base system with the most important things already installed and set up correctly.

Why should I use baseimage-docker?

Why use baseimage-docker instead of doing everything yourself in Dockerfile?

• It reduces the time needed to write a correct Dockerfile. You won't have to worry about the base system and can focus on your stack and your app.
• It sets up the base system correctly. It's very easy to get the base system wrong, but this image does everything correctly.

Contents

Component	Why is it included? / Remarks
Ubuntu 12.04 LTS	The base system.
A correct init process	According to the Unix process model, the init process -- PID 1 -- inherit all orphaned child processes and must reap them. Most Docker containers do not have an init process that does this correctly, and as a result their containers become filled with zombie processes over time. Baseimage-docker comes with an init process /sbin/my_init that performs reaping correctly.
Fixes APT incompatibilities with Docker	See https://github.com/dotcloud/docker/issues/1024.
syslog-ng	A syslog daemon is necessary so that many services - including the kernel itself - can correctly log to /var/log/syslog. If no syslog daemon is running, a lot of important messages are silently swallowed. Only listens locally.
ssh server	Allows you to easily login to your container to inspect or administer things. Password and challenge-response authentication are disabled by default. Only key authentication is allowed. It allows an predefined key by default to make debugging easy. You should replace this ASAP. See instructions.
runit	For service supervision and management. Much easier to use than SysV init and supports restarting daemons when they crash. Much easier to use and more lightweight than Upstart.

Using baseimage-docker as base image

The image name is phusion/baseimage. Here's how your Dockerfile may look like:

# Use phusion/baseimage as base image. To make your builds reproducible, make
# sure you lock down to a specific version, not to `latest`!
FROM phusion/baseimage:<VERSION>

# Remove authentication rights for insecure_key.
RUN rm -f /root/.ssh/authorized_keys /home/*/.ssh/authorized_keys

# Use baseimage-docker's init process.
CMD ["/sbin/my_init"]

# ...put other build instructions here...

# Clean up APT when done.
RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*