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Ushahidi Docker OS images

These are base OS images with useful tools baked in (details below).

We offer Debian and Alpine images.

Wrapper for dockerize

github.com/jwilder/dockerize is a utility to perform some commonplace container customisations on initialisation.

These customisations include rendering configuration files from a template (i.e. to include values of environment variables) and waiting for other services to be ready.

This wrapper enables the container image developer to configure all these customisations via creation of files and setting environment variables.

  • DOCKERIZE_TEMPLATE_DIR : this directory will be searched for files to pass as templates to dockerize. The destination path is determined from the template path inside the directory, thus a file in this path:

    $DOCKERIZE_TEMPLATE_DIR/etc/config.file

    will configure the container to process that file as a template when the container gets started, and write the results on /etc/config.file

    The wrapper will attempt to create the destination folder if it doesn't exist.

    This environment variable defines to /tmpl

  • DOCKERIZE_WAIT_* : the values of any environment variables with names matching this pattern will be passed as -wait options to dockerize. i.e. DOCKERIZE_WAIT_MYSQL=tcp://mysql:3306

CES (Chained Entrypoint Scripts)

As a bonus, we add Chained Entrypoint Script logic to easily customize and extend the container startup sequence.

Entrypoint scripts usually deal with container initialization and parsing / processing of the container command and arguments. Docker provides means for setting the container entrypoint, but no means for extending that entrypoint as other Dockerfiles build on top of an image.

CES helps Dockerfile authors easily build an initialization chain

In order for entrypoint scripts to be chainable, they should finish their execution with something functionally similar to exec "$@"

Setting up CES

The following Dockerfile statements install and set up CES

ENV DOCKERCES_MANAGE_UTIL=/manage.CES.sh \
    DOCKERCES_ENTRYPOINT_CHAIN=/entrypoints.CES \
    DOCKERCES_ENDPOINT_FILE=/endpoint.CES \
    DOCKERCES_ENTRYPOINT=/entrypoint.CES.sh \
    DOCKERCES_DEBUG=1
COPY /entrypoint.CES.sh $DOCKERCES_ENTRYPOINT
RUN ln -s /entrypoint.CES.sh $DOCKERCES_MANAGE_UTIL
ENTRYPOINT [ "/bin/bash", "/entrypoint.CES.sh" ]

Management mode

From the Dockerfile, we invoke the CES script in management mode. The purpose of doing so is to modify / extend the startup chain. i.e.:

COPY entrypoint.dockerize.sh /entrypoint.dockerize.sh
RUN $DOCKERCES_MANAGE_UTIL add /entrypoint.dockerize.sh

has the effect of adding the /entrypoint.dockerize.sh to the chain of entrypoints

COPY run.sh /run.sh
RUN $DOCKERCES_MANAGE_UTIL endpoint /run.sh

has the effect of setting /run.sh as the endpoint of the initialization chain. There can only be one endpoint and it's always executed at the end of the chain. Thus, it doesn't need to be chainable.