When testing Docker and iptables I stumbled upon something interesting. It appears Docker uses the iptables INPUT chain in an undocumented way. Well that’s interesting..
If you’ve ever used Docker, you’ve probably used the latest Docker image tag. This is bad. Do not do this! You will be in a situation where you need to find what version you were actually using. This is how you can find the version of that “latest” image you have running.
Using a dynamic Dockerfile can have great benefits when used in your CI/CD pipeline. You can use the ARG statement in your Dockerfile to pass in a variable at build time. Even use a variable in the FROM statement!