$ sudo apt-get install xorg-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package xorg-server

ii  xserver-common 2:1.16.1.901 all          common files used by various X se
ii  xserver-xorg   1:7.7+7ubunt amd64        X.Org X server
ii  xserver-xorg-c 2:1.16.1.901 amd64        Xorg X server - core server
rc  xserver-xorg-c 2:1.16.0-1ub amd64        Xorg X server - core server

Build Date: 12 February 2015  02:46:23PM
xorg-server 2:1.16.0-1ubuntu1.3 (For technical support please see h
ttp://www.ubuntu.com/support)