Simple way, in order to make a screenshot in Centos 6.x
[rx@localhost ~]$ cat /etc/redhat-release
CentOS release 6.8 (Final)
[rx@localhost ~]$ uname -a
Linux localhost.localdomain 2.6.32-573.el6.x86_64 #1 SMP Thu Jul 23 15:44:03 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
[rx@localhost ~]$ su -
Install this by typing:
yum install gnome-utils
S a m p l e of Screnshoot: