.docker/Dockerfile|12 col 1| Do not refer to an environment variable within the same ENV statement where it is defined.
.docker/Dockerfile|30 col 1| Pin versions in apt get install. Instead of apt-get install <package> use apt-get install <package>=<version>
.docker/Dockerfile|30 col 1| Set the SHELL option -o pipefail before RUN with a pipe in it. If you are using /bin/sh in an alpine image or if your shell is symlinked to busybox then consider explicitly setting your SHELL to /bin/ash, or disable this check
.docker/Dockerfile|54 col 1| Pin versions in gem install. Instead of gem install <gem> use gem install <gem>:<version>