In Ubuntu 12.04 and maybe others, if we set displays for multiple monitor it just works for the current session. It means, if we restart our PC, the setting was gone and we need to set up again via display setting as shown from the picture below.
|Ubuntu Display Setting|
To store permanently the multiple monitors setting in Ubuntu, we can manually set the xrandr by making file .xprofile in home directory (~/.xprofile). For example, to set extra monitor in the left side of main monitor permanently (as shown by the picture above), type the following in ~/.xprofile
xrandr –output VGA1 –left-of LVDS1
|Extra monitor on the left of main monitor as set in ~/.xprofile|