How can I configure `anybody` to run X in a one-liner?

Question

The common solution posted is to run sudo dpkg-reconfigure x11-common which gives a graphical prompt, however, I'm wanting to use this non-interactively.

Scenario is that I'm SSH'd into a machine as root (during Vagrant provisioning) and need to run startx once as a regular user to generate some config files before proceeding to subsequent steps.

I believe the reason I cannot simply su otheruser startx is due to Xauthority/me being connected via SSH as another user...

Solution

The solution I found was to run the following:

sudo sed -i \
    's/allowed_users=console/allowed_users=anybody/' /etc/X11/Xwrapper.config

Note, that in your situation, the console may be root or another, based on your particular initial configuration*

Comments

[Sebastian]

convincing X to drop root privileges is a rather new feature (xorg 1.16.0 iirc). Details are found in man Xorg.wrap.

[imsodin]

On debian the configuration file "Xwrapper.config" may be present, while the package xserver-xorg-legacy is not installed. In this case it has no effect, so the problems persist after changing the configuration.