If there’s one use-case that Docker’s repeatedly proven itself on (to me, anyway), it’s the ability to run really old software in a modern environment. The chaos monkey/hyperscale stuff is nice, but:

FROM jeanblanchard/java:jre-7

COPY BuiltIn2012.jar /server.jar


CMD ["/opt/jre/bin/java", "-Xmx300m", "-jar", "/server.jar"]

That’s magic.

A real lifesaver when one of your projects involves running an app last maintained in 2014 (PHP 5.3, MySQL 5.5, and Java 1.7) – turns out there are absolute legends out there maintaining images for these really old versions of things, making it trivial to spin up legacy applications on modern hardware.