I have a hard-wired (i.e not multiplex) Nvidia GeForce 540m discrete GPU with an integrated Intel graphics card.

I have no need for the discrete graphics card and am trying to disable it completely (at the moment, they are both powered on).

I am familiar with HybridGraphics on Ubuntu and the various on/off commands, and read these two posts to help me achieve this

How to permanently switch off discrete graphic card?

and this from UbuntuGuide.

Unfortunately, both the tutorials suggest editing /etc/rc.local file by adding switcheroo commands. I have tried this and my system completely refuses to boot when I edit the rc.local; I had to restore the original file to regain access Ubuntu.

Are there other methods which I can use to disable my GPU safely?