在测试服务器（Red Hat Enterprise Linux Server release 6.6）需要安装桌面系统环境，于是选择GNOME桌面环境安装。
一：检查系统的运行级别以及是否安装了桌面环境
[root@localhost ~]# runlevel
N 3
[root@localhost ~]# yum grouplist | more
Loaded plugins: product-id, security, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-
manager to register.
Setting up Group Process
Installed Groups:
Additional Development
Base
Console internet tools
Directory Client
E-mail server
Fonts
Graphical Administration Tools
Hardware monitoring utilities
Java Platform
Large Systems Performance
Legacy UNIX compatibility
Legacy X Window System compatibility
NFS file server
Network file system client
Networking Tools
PHP Support
Performance Tools
Perl Support
Scientific support
Security Tools
Server Platform
System Management
System administration tools
TurboGears application framework
Web Server
也可以使用下面命令验证是否安装桌面环境组件
[root@localhost ~]# ps -A | egrep -i "gnome|kde|mate|cinnamon|lx|xfce|jwm"
[root@localhost ~]#
二：安装桌面环境相关软件组
使用yum grouplist 可以看到有Desktop、Desktop Platfrom、X Window System、Graphics Creation Tools等桌面环境有关的软件组件可以安装
[root@localhost ~]# yum groupinstall "Desktop" "Desktop Platform"
[root@localhost ~]# yum groupinstall "X Window System" "Graphics Creation Tools"
三：修改系统的启动级别为 5
[root@localhost ~]# vi /etc/inittab
# inittab is only used by upstart for the default runlevel.
#
# ADDING OTHER CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
#
# System initialization is started by /etc/init/rcS.conf
#
# Individual runlevels are started by /etc/init/rc.conf
#
# Ctrl-Alt-Delete is handled by /etc/init/control-alt-delete.conf
#
# Terminal gettys are handled by /etc/init/tty.conf and /etc/init/serial.conf,
# with configuration in /etc/sysconfig/init.
#
# For information on how to write upstart event handlers, or how
# upstart works, see init(5), init(8), and initctl(8).
#
# Default runlevel. The runlevels used are:
# 0 - halt (Do NOT set initdefault to this)
# 1 - Single user mode
# 2 - Multiuser, without NFS (The same as 3, if you do not have networking)
# 3 - Full multiuser mode
# 4 - unused
# 5 - X11
# 6 - reboot (Do NOT set initdefault to this)
#
id:3:initdefault:
将系统的启动级别从3修改为5，然后重启系统后，重启过后出现下面界面，按照提示操作即可。操作完成后重启系统即OK。
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