一.Linux的运行级别
1.查看当前运行级别的命令：runlevel
2.每个运行级别的作用
二.各运行级别下的含义
1.init 0（关机）
# ls /etc/rc.d/rc0.d
K05wdaemon K60crond K84NetworkManager K90network
K10saslauthd K73winbind K84wpa_supplicant K92ip6tables
K15svnserve K74haldaemon K85mdmonitor K92iptables
K25sshd K74ntpd K85messagebus K95firstboot
K30postfix K75netfs K87restorecond S00killall
K30spice-vdagentd K75ntpdate K88auditd S01halt
K50dnsmasq K75udev-post K88rsyslog
K50netconsole K80kdump K89rdisc
这个级别启动的只有killall和hatl服务，杀死全部进程和关机，这个级别只用作关机
2.init 1（单用户模式）
# ls /etc/rc.d/rc1.d
K05wdaemon K60crond K84wpa_supplicant K92ip6tables
K10saslauthd K73winbind K85mdmonitor K92iptables
K15svnserve K74haldaemon K85messagebus K95firstboot
K25sshd K74ntpd K87restorecond S26udev-post
K30postfix K75netfs K88auditd S99single
K30spice-vdagentd K75ntpdate K88rsyslog
K50dnsmasq K80kdump K89rdisc
K50netconsole K84NetworkManager K90network
这个级别启动的服务同样只有两个，udev相关和single(单用户模式)。只支持root单用户，不支持其 他用户使用
3.init 2（多用户模式-无fns）
# ls /etc/rc.d/rc2.d
K05wdaemon K74ntpd S08ip6tables S26udev-post
K10saslauthd K75netfs S08iptables S55sshd
K15svnserve K75ntpdate S10network S80postfix
K30spice-vdagentd K80kdump S11auditd S90crond
K50dnsmasq K84wpa_supplicant S12rsyslog S99local
K50netconsole K87restorecond S15mdmonitor
K73winbind K89rdisc S22messagebus
K74haldaemon K95firstboot S23NetworkManager
这个级别启动服务很多， 基本上需要的都有，但是nfs相关服务没有开启，这个级别不支持nfs
4.init 3（多用户模式）
# ls /etc/rc.d/rc3.d
K05wdaemon K75ntpdate S11auditd S26udev-post
K10saslauthd K84wpa_supplicant S12rsyslog S55sshd
K15svnserve K87restorecond S15mdmonitor S80postfix
K30spice-vdagentd K89rdisc S20kdump S90crond
K50dnsmasq K95firstboot S22messagebus S99local
K50netconsole S08ip6tables S23NetworkManager
K73winbind S08iptables S25netfs
K74ntpd S10network S26haldaemon
服务基本开启，nfs服务也有了，我们平时运行虚拟机默认的启动级别也是这个级别
5.init 4（保留级别）
# ls /etc/rc.d/rc4.d
K05wdaemon K75ntpdate S11auditd S26udev-post
K10saslauthd K84wpa_supplicant S12rsyslog S55sshd
K15svnserve K87restorecond S15mdmonitor S80postfix
K30spice-vdagentd K89rdisc S20kdump S90crond
K50dnsmasq K95firstboot S22messagebus S99local
K50netconsole S08ip6tables S23NetworkManager
K73winbind S08iptables S25netfs
K74ntpd S10network S26haldaemon
开启的服务和init3是一样一样滴，所以这只是作为一个保留的级别（并不是安全模式！）
6.init 5（图形界面）
# ls /etc/rc.d/rc5.d
K05wdaemon K84wpa_supplicant S12rsyslog S55sshd
K10saslauthd K87restorecond S15mdmonitor S70spice-vdagentd
K15svnserve K89rdisc S20kdump S80postfix
K50dnsmasq K95firstboot S22messagebus S90crond
K50netconsole S08ip6tables S23NetworkManager S99local
K73winbind S08iptables S25netfs
K74ntpd S10network S26haldaemon
K75ntpdate S11auditd S26udev-post
我并没有安装图形界面，所有我也不是很清楚
7、init 6（重新启动）
# ls /etc/rc.d/rc6.d
K05wdaemon K60crond K84NetworkManager K90network
K10saslauthd K73winbind K84wpa_supplicant K92ip6tables
K15svnserve K74haldaemon K85mdmonitor K92iptables
K25sshd K74ntpd K85messagebus K95firstboot
K30postfix K75netfs K87restorecond S00killall
K30spice-vdagentd K75ntpdate K88auditd S01reboot
K50dnsmasq K75udev-post K88rsyslog
K50netconsole K80kdump K89rdisc
只有一个killall和一个reboot reboot（重新启动）
三.安装图形界面
1.首先用yum grouplist查看可用的安装软件包；
2.因为并不支持中文（我不服），所以要转化成英文：LANG=en；
3.安装Desktop和window system；
yum grouplist -y "X Window System"
yum grouplist -y "Desktop"
这样图形界面就安装成功，大功告成了