But what if we want to add files that live outside of the container that might need to persist even when the container dies? That is where the VOLUME directive comes into play. With VOLUMEs, any time you start the container, this path is actually assumed to be mounted from outside of the container, and if none is provided, one will be created and attached for you automatically.

Here, we are assigning our /srv/www/html/external path to this unnamed volume, but we will reserve majority of our detailed discussion about volumes for later chapters.