Hey @ajmuir ,
I know you solved your problem over a year ago but I wanted to add my two cents to this discussion and also enable new users who find this thread to drive down the right path.
Webdock (now) recommends using fuse-overlayfs as the Docker storage driver to use: How to change the Docker storage driver – Webdock
Reason being that vfs produces high disk space usage.
But using fuse-overlayfs for Docker will produce a warning or an error on the Discourse launcher side, since it is not a recommended driver.
I have detailed instructions on how to solve this in this post on my blog: Deploying Discourse on a Webdock server
You can also do it the way you did by adding the installed driver to the egrep statement.
And why do you say that Webdock doesn’t allow the creation of root users?
You can simply switch to root with sudo su and execute the commands from the Discourse install guide after that.