Disabling laptop monitor on boot?

I managed to find a fix for my problem. I simply added this to my /etc/default/grub file:

GRUB_CMDLINE_LINUX_DEFAULT="<default paramaters> video=LVDS-1:d"

Then did a good ol' fashin update-grub.

This disabled the laptop's LCD on boot, and allowed the external monitor to automatically set its resolution, which worked without a hitch.

If your kernel has i915 driver enabled, the following (which I quote from ArchLinux Wiki, and which in turn quotes from nouveau wiki) might prove helpful.

Basically you could experiment with adding video=... parameter in grub using the d option (see the parameter format below) to disable the internal monitor (whichever name it might have for <conn> option you need to find from the system log which should display the available options during kernel start-up. The information might still be available from previous start-up in /var/log/dmesg if your distro has that, please try grep i915 /var/log/dmesg* and post it here.

https://wiki.archlinux.org/index.php/Kernel_Mode_Setting:

A mode can be forced on the kernel command line. Unfortunately, the command line option video is poorly documented in the DRM case. Bit and pieces on how to use it can be found in

http://cgit.freedesktop.org/nouveau/linux-2.6/tree/Documentation/fb/modedb.txt
http://cgit.freedesktop.org/nouveau/linux-2.6/tree/drivers/gpu/drm/drm_fb_helper.c

The format is:

video=<conn>:<xres>x<yres>[M][R][-<bpp>][@<refresh>][i][m][eDd]

<conn>: Connector, e.g. DVI-I-1, see your kernel log.
<xres> x <yres>: resolution
M: compute a CVT mode?
R: reduced blanking?
-<bpp>: color depth
@<refresh>: refresh rate
i: interlaced (non-CVT mode)
m: margins?
e: output forced to on
d: output forced to off
D: digital output forced to on (e.g. DVI-I connector) 

You can override the modes of several outputs using "video" several times, for instance, to force DVI to 1024x768 at 85 Hz and TV-out off:

video=DVI-I-1:1024x768@85 video=TV-1:d