Cannot execute RUN mkdir in a Dockerfile

When creating subdirectories hanging off from a non-existing parent directory(s) you must pass the -p flag to mkdir ... Please update your Dockerfile with

RUN mkdir -p ... 

I tested this and it's correct.

The problem is that /var/www doesn't exist either, and mkdir isn't recursive by default -- it expects the immediate parent directory to exist.

Use:

mkdir -p /var/www/app

...or install a package that creates a /var/www prior to reaching this point in your Dockerfile.

You can also simply use

WORKDIR /var/www/app

It will automatically create the folders if they don't exist.

Then switch back to the directory you need to be in.