Bash Container

Common container Bash functions used for handling Docker image entrypoint semantics.

All functions are Bats tested and checked against ShellCheck.

Install

The main functions require bash, curl and coreutils. These take about 10M of space. The template function requires gomplate.

Debian

# Install bash-container functions
RUN set -x \
  && BASHCONTAINER_VERSION=0.8.0 \
  && BASHCONTAINER_SHA256=0ddc93b11fd8d6ac67f6aefbe4ba790550fc98444e051e461330f10371a877f1 \
  && if ! command -v wget > /dev/null; then \
      fetchDeps="${fetchDeps} wget"; \
     fi \
  && apt-get update \
  && apt-get install -y --no-install-recommends ca-certificates curl ${fetchDeps} \
  && cd /tmp \
  && wget -nv https://github.com/panubo/bash-container/releases/download/v${BASHCONTAINER_VERSION}/panubo-functions.tar.gz \
  && echo "${BASHCONTAINER_SHA256}  panubo-functions.tar.gz" > /tmp/SHA256SUM \
  && ( cd /tmp; sha256sum -c SHA256SUM || ( echo "Expected $(sha256sum panubo-functions.tar.gz)"; exit 1; )) \
  && tar --no-same-owner -C / -zxf panubo-functions.tar.gz \
  && rm -rf /tmp/* \
  && apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false ${fetchDeps} \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/* \
  ;

Alpine

# Install bash-container functions
RUN set -x \
  && BASHCONTAINER_VERSION=0.8.0 \
  && BASHCONTAINER_SHA256=0ddc93b11fd8d6ac67f6aefbe4ba790550fc98444e051e461330f10371a877f1 \
  && if [ -n "$(readlink /usr/bin/wget)" ]; then \
      fetchDeps="${fetchDeps} wget"; \
     fi \
  && apk add --no-cache ca-certificates bash curl coreutils ${fetchDeps} \
  && cd /tmp \
  && wget -nv https://github.com/panubo/bash-container/releases/download/v${BASHCONTAINER_VERSION}/panubo-functions.tar.gz \
  && echo "${BASHCONTAINER_SHA256}  panubo-functions.tar.gz" > /tmp/SHA256SUM \
  && ( cd /tmp; sha256sum -c SHA256SUM || ( echo "Expected $(sha256sum panubo-functions.tar.gz)"; exit 1; )) \
  && tar --no-same-owner -C / -zxf panubo-functions.tar.gz \
  && rm -rf /tmp/* \
  && apk del ${fetchDeps} \
  ;

Example Usage

The functions are used within a Docker entrypoint script to simplify container initialization and abstract entrypoints.

This example also uses a Mountfile and Procfile.

#!/usr/bin/env bash

set -e

source /panubo-functions.sh

# Wait for services
wait_mariadb "${DB_HOST}" "${DB_PORT:-3306}"

# Mount data mounts (specifying an alternate mount point uid/gid)
MOUNTFILE_MOUNT_UID=33
MOUNTFILE_MOUNT_GID=33
run_mountfile

# Exec Procfile command, or if not found in Procfile execute the command passed to the entrypoint
exec_procfile "${1}" || exec "$@"

Alternate Procfile handling:

# Try to run a procfile command
exec_procfile "$1"

# exec_procfile returns 127 if the command isn't in the Procfile
if [ "$?" -eq "127" ]; then
	exec "${@}"
fi

Using gomplate templating

Add to your Dockerfile, to install gomplate (Debian example):

# Install gomplate
RUN set -x \
  && GOMPLATE_VERSION=3.8.0 \
  && GOMPLATE_SHA256=847f7d9fc0dc74c33188c2b0d0e9e4ed9204f67c36da5aacbab324f8bfbf29c9 \
  && if ! command -v wget > /dev/null; then \
      fetchDeps="${fetchDeps} wget"; \
     fi \
  && apt-get update \
  && apt-get install -y --no-install-recommends ca-certificates ${fetchDeps} \
  && wget -nv -O /tmp/gomplate_linux-amd64-slim -L https://github.com/hairyhenderson/gomplate/releases/download/v${GOMPLATE_VERSION}/gomplate_linux-amd64-slim \
  && echo "${GOMPLATE_SHA256}  gomplate_linux-amd64-slim" > /tmp/SHA256SUM \
  && ( cd /tmp; sha256sum -c SHA256SUM; ) \
  && mv /tmp/gomplate_linux-amd64-slim /usr/local/bin/gomplate \
  && chmod +x /usr/local/bin/gomplate \
  && rm -rf /tmp/* \
  && apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false ${fetchDeps} \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/* \
  ;

Or add to your Dockerfile, to install gomplate (Alpine example):

# Install gomplate
RUN set -x \
  && GOMPLATE_VERSION=3.8.0 \
  && GOMPLATE_SHA256=847f7d9fc0dc74c33188c2b0d0e9e4ed9204f67c36da5aacbab324f8bfbf29c9 \
  && cd /tmp \
  && wget -nv https://github.com/hairyhenderson/gomplate/releases/download/v${GOMPLATE_VERSION}/gomplate_linux-amd64 \
  && echo "${GOMPLATE_SHA256}  gomplate_linux-amd64" > /tmp/SHA256SUM \
  && ( cd /tmp; sha256sum -c SHA256SUM || ( echo "Expected $(sha256sum gomplate_linux-amd64)"; exit 1; )) \
  && chmod +x gomplate_linux-amd64 \
  && mv gomplate_linux-amd64 /usr/local/bin/gomplate \
  && rm -rf /tmp/* \
  ;

A minimal template (/foo.conf.tmpl):

# Template example
FOO={{ getenv "MYAPP_FOO" "default_foo_value" }}

A minimal entrypoint script:

#!/usr/bin/env bash

set -e

source /panubo-functions.sh

render_templates /foo.conf.tmpl

This will render /foo.conf.tmpl to /foo.conf.

Bash Strict Mode

Although we like Unofficial Bash Strict Mode not all of these functions currently work under strict mode.