CentOS 7.2.1511
方案1：使用 gnome shell extensions
安装扩展：Topicons
参考：
http://linuxsoft.cern.ch/cern/centos/7/updates/x86_64/repoview/gnome-shell-extension-top-icons.html
下载：gnome-shell-extension-top-icons-3.14.4-13.el7.noarch.rpm（http://linuxsoft.cern.ch/cern/centos/7/updates/x86_64/Packages/gnome-shell-extension-top-icons-3.14.4-13.el7.noarch.rpm）
安装：rpm -ivh gnome-shell-extension-top-icons-3.14.4-13.el7.noarch.rpm
安装完之后，按Alt+F2，输入r，回车。
使能：
Applications -> Utilities -> Tweak tool -> extensions，使能Top icons
方案2：使用 mate desktop
参考：centos 7安装mate桌面
下载了最新的centos7适用了下，记录了下安装过程。
安装略过. 只选择最小化安装
重启,登录
yum install net-tools
在mate官网中 http://wiki.mate-desktop.org/download 这个地址中,有RHEL7安装mate方法
Red Hat Enterprise Linux 7
MATE is available through the Extra Packages for Enterprise Linux (EPEL) （https://fedoraproject.org/wiki/EPEL）repository, maintained by the Fedora Project. This should work on CentOS 7 as well, and any other compatible derivatives.
After you install the epel-release-7*.rpm package to add the EPEL repository to Yum, you can install MATE with the following command:
yum groups install "MATE Desktop"
If you install this on a minimal system without an existing GUI configured (such as a GNOME or KDE desktop), you might want to install the X Window System group as well for local graphical logins:
yum groups install "X Window System"
you may also want to change the default systemd target to graphical:
systemctl set-default graphical.target
由于是最小化安装,需要先去 https://fedoraproject.org/wiki/EPEL 扩展包. 有下载地址
If you are running an EL7 beta version, please visit here to get the newest 'epel-release' package for EL7: The newest version of 'epel-release' for EL7（http://download.fedoraproject.org/pub/epel/beta/7/x86_64/repoview/epel-release.html）
选择下载地址.可以知道网络地址
然后 rpm -ivh http://mirrors.hustunique.com/epel/beta/7/x86_64/epel-release-7-0.2.noarch.rpm
然后
yum groups install "MATE Desktop"
yum groups install "X Window System"
systemctl set-default graphical.target
简要方法：下载：https://mirrors.tuna.tsinghua.edu.cn/epel/7/x86_64/e/epel-release-7-6.noarch.rpm
执行：
rpm -vih epel-release-7-6.noarch.rpm
yum groups install “MATE Desktop” // 注意：是英文的引号；这个安装执行时间比较长。
yum groups install “X Window System” // 注意：是英文的引号
systemctl set-default graphical.target
然后logout，登录时选择mate desktop。