[ubuntu] How to kill X server without rendering computer insert

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http://ubuntuforums.org – I have a Ubuntu 12.04 box with a new Nvidia GeForce GTX 680 video card. I can't install the linux video driver for that card, because the installer stops when it detects an X server active, & refuses to proceed. If I use "dmlight stop" (or something near that, I forget the syntax) it kills X, but in replacement I have a monochrome blank screen. No console, no nothing, so I can't start anything, let alone the video card driver installer. I also monkeyed with fstab & told it to boot to runlevel 1 (I think it was---it's supposed to be console only) and my machine looked up (Hardware)