The Graphic User Interface is very useful but it consumes a lot of CPU power.
In many cases the GUI is useless so I disable it.
With Ubuntu 14.04 you can disable the startup of the GUI at boot time, simply changing the grub configuration.

 

grub

 
Open a new terminal.

Make a copy of the grub file, so you can restore your previous version…..

# cp -n /etc/default/grub /etc/default/grub.orig

Edit the grub configuration file with your favourite text editor (I use vim…)
# vim /etc/default/grub

Comment the line containing the GRUB_CMDLINE_LINUX_DEFAULT declaration by adding a # at the beginning of the line, you shoud have something like the following:
#GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash”

Change GRUB_CMDLINE_LINUX=”” to GRUB_CMDLINE_LINUX=”text”

Uncomment the line
#GRUB_TERMINAL=console
removing the # at the beginning.

Save the changes and exit from the text editor

Udate the grub
# update-grub

Reboot your system.

Gg1