DockerEntrypoint

• Example entry point file
  • It creates a env.js file form environment variables - for use with SPA react/angular for runtime config

  • Add to Dockerfile as

    COPY Dockerentrypoint.sh /Dockerentrypoint.sh
    ENTRYPOINT [ "/Dockerentrypoint.sh" ]

  • at the last line it executes Docker CMD passed to docker

# Container startups script.
# Allow for runtime configuration through env vars.
# https://12factor.net/build-release-run
set -e
echo "# Start container with $0  PWD=${PWD}"
echo "#"

echo "# cat .version.txt"
cat .version.txt
echo "#"

echo "# Add env vars REACT_APP_* to ''env.js'' at webserver root"
echo "window.ENV = `jo -p \`env | grep REACT_APP_ | sed -e 's/[[:blank:]]/{_!!_}/g'\` end=1`" | sed -e 's/{_!!_}/ /g' | tee env.js
echo "#"

echo "# Starting docker cmd \$@=$@ ..."
exec "$@"

• AWS ECS docker entrypoint.sh script to add metadata on startup to .version.txt

  # Container startups script.
  # Allow for runtime configuration through env vars.
  # https://12factor.net/build-release-run
  set -e
  echo "# Start container with $0  PWD=${PWD}"
  echo "#"
  
  # Get aws ecs container metadata, add to .version.txt if available.
  if [[ -z "${ECS_CONTAINER_METADATA_URI_V4}" ]]; then
      echo "# Not running in ECS, probably local." | tee -a .version.txt
  else
      echo "# aws ecs extracting metadata." | tee -a .version.txt
          echo "# curl -s ${ECS_CONTAINER_METADATA_URI_V4}" >> .version.txt
          curl -s "${ECS_CONTAINER_METADATA_URI_V4}" >> .version.txt || true
          echo "# aws ecs - The END." >> .version.txt
  fi
  
  echo "# cat .version.txt"
  cat .version.txt
  echo "#"
  
  echo "# Add env vars REACT_APP_* to ''env.js'' at webserver root"
  echo "export default () => (`jo -p \`env | grep REACT_APP_ | sed -e 's/[[:blank:]]/{_!!_}/g'\` end=1`)" | sed -e 's/{_!!_}/ /g' | tee env.js
  echo "#"
  
  echo "# Starting docker cmd \$@=$@ ..."
  exec "$@"

docker run override entrypoint

• put --entrypoint just after run

  docker run --entrypoint <entrypoint.sh> <image:tag> <arg1> <arg2> <arg3>