How do I set the Apache2 DocumentRoot to a "vboxsf" VirtualBox Shared Folder? (permissions issue?)

It would probably be easiest to add the vboxsf group as a supplementary group for apache.

Ubuntu:

sudo usermod -a -G vboxsf www-data

Fedora:

sudo usermod -a -G vboxsf apache

This does it for me when I want to access auto mounted shared folders. You might also want to add your own username to the vboxsf group to access the files.

That looks like a permissions issue. You'll need read and execute permission on /media/sf_Dev/ for "other" (the third group of permission bits, which are currently no permissions or ---).

So, you'll need to run this command (since it's Ubuntu, note the sudo):

sudo chmod 775 /media/sf_Dev/

That will add read and execute for "other" and leave full permissions for owner and group.

Also make sure that the index file actually exists in /media/sf_Dev/. (I'll assume that you forgot the sudo in the cp command and that you're not running as root.)

You didn't say what the specific error was, only

and Apache doesn't seem to see the index.html I put in that directory

The specific error would help. You can file this in Apache's error_log, which is typically under /var/log/apache2/error.log under Ubunt, but can be configured via an ErrorLog Directive in your <VirtualHost>

Without the actual error, I assume George Marian is correct and it's a permissions error. You can check to see what group Apache is running under using:

ps -o pid,group -o atime,comm=CMD awx | grep apache

Try chainging permissions on /media/sf_Dev/ as he said.

I think you may better off handling this with an Alias directive as that will allow you to make only certain parts of your DocumentRoot point to locations outside:

Alias /info /media/sf_Dev
<Directory /media/sf_Dev >
  Order allow,deny
  Allow from all
</Directory>

EDIT: If the Apache server has mod_php (not FastCGI PHP) and is not using suexec, you can determine if Apache is running under the proper GID (group ID) with the following PHP snippit:

<?php

var_dump(posix_getegid());

Make sure that returns the same GID as vboxsf. (You can find the GID for vboxsf in /etc/groups)