启动级别:init 0,1,2,3,4,5,6
0:停机1：单用户形式，只root进行维护2：多用户，不能使用net file system3：完全多用户5：图形化4：安全模式6：重启??其实，可以通过查看/etc/rc.d/中的rc*.d的文件来对比理解。。init 0，对应的系统会运行，/etc/rc.d/rc0.d里指定的程序。我们来看下名称。[root@localhost ?～]# ls?/etc/rc.d/rc0.d?K01dnsmasq ???K15ksmtuned ?K35nmb ????????K60crond ??????K74lm_sensors ?K83portreserve ???K85rpcgssd ???K88iscsi ????K90network ??????S00killallK10cups ??????K16ksm ??????K35smb ????????K66gpsd ???????K75netfs ??????K84NetworkManager ?K85rpcidmapd ?K88rsyslog ??K92ip6tables?????S01haltK10saslauthd ?K20nfs ??????K36mysqld ?????K69rpcsvcgssd ?K75udev-post ??K84wpa_supplicant ?K86nfslock ???K89iscsid ???K92iptablesK10xfs ???????K25sshd ?????K50haldaemon ??K70vboxdrv ????K76openvpn ????K85mdmonitor ?????K87alsasound ?K89netplugd ?K98qemuK15gpm ???????K30sendmail ?K50netconsole ?K74acpid ??????K83bluetooth ??K85messagebus ?????K87rpcbind ???K89rdisc ????K99lvm2-monitor依照上述红色字体，开机会执行的两个进程是killall和halt，这两个都表示为终止进程。故init 0是用于表示关机的。?init 1，对应的系统会运行，/etc/rc.d/rc1.d里指定的程序。[root@localhost ～] # ls /etc/rc.d/rc1.dK01dnsmasq ???K15ksmtuned ?K35nmb ????????K60crond ??????K74lm_sensors ??K84NetworkManager ?K85rpcidmapd ?K88rsyslog ??K92ip6tables ????S99singleK10cups ??????K16ksm ??????K35smb ????????K66gpsd ???????K75netfs ???????K84wpa_supplicant ?K86nfslock ???K89iscsid ???K92iptablesK10saslauthd ?K20nfs ??????K36mysqld ?????K69rpcsvcgssd ?K76openvpn ?????K85mdmonitor ?????K87alsasound ?K89netplugd ?K98qemuK10xfs ???????K25sshd ?????K50haldaemon ??K70vboxdrv ????K83bluetooth ???K85messagebus ?????K87rpcbind ???K89rdisc ????S02lvm2-monitorK15gpm ???????K30sendmail ?K50netconsole ?K74acpid ??????K83portreserve ?K85rpcgssd ???????K88iscsi ?????K90network ??S26udev-post这个级别启动的服务有三个，udev、lvm相关的和single(单用户模式的服务)。故此级别是单用户模式，只有root能用，不支持其他用户。?init 2，对应的系统会运行，/etc/rc.d/rc2.d里指定的程序。[root@localhost ~ ]# ls /etc/rc.d/rc2.d/K01dnsmasq ???K20nfs ??????K36mysqld ?????K74lm_sensors ?????K85rpcgssd ???K89netplugd ?????S08iptables ???S23NetworkManager ?S30vboxdrv ???S99localK10saslauthd ?K25sshd ?????K50haldaemon ??K75netfs ??????????K85rpcidmapd ?K89rdisc ???????S12rsyslog ????S24portreserve ????S35qemuK10xfs ???????K30sendmail ?K50netconsole ?K76openvpn ????????K86nfslock ???K90network ?????S13rpcbind ????S25cups ???????????S85gpmK15ksmtuned ??K35nmb ??????K66gpsd ???????K83bluetooth ??????K88iscsi ?????S02lvm2-monitor ?S15mdmonitor ??S26acpid ??????????S90crondK16ksm ???????K35smb ??????K69rpcsvcgssd ?K84wpa_supplicant ?K89iscsid ????S08ip6tables ???S22messagebus ?S26udev-post ??????S99alsasound这个级别启动的服务多了，NetworkManager/iptables/acpid/alsa都已经开启，但是nfs,smb,openvpn相关服务没有开启，这个级别不支持nfs。?init 3 ， 对应的系统运行/etc/rc.d/rc3.d[root@localhost ~] # ls /etc/rc.d/rc3.d/K01dnsmasq ???K30sendmail ???K74lm_sensors ?????K89rdisc ????????S08iptables ?S18rpcidmapd ?????S25cups ??????S35qemu ??????S85ksmtuned ??S99localK10saslauthd ?K36mysqld ?????K76openvpn ????????K90network ??????S12rsyslog ??S19rpcgssd ???????S25netfs ?????S50bluetooth ?S90crondK10xfs ???????K50netconsole ?K84wpa_supplicant ?K99lvm2-monitor ?S13iscsi ????S22messagebus ?????S26acpid ?????S50haldaemon ?S91nmbK20nfs ???????K66gpsd ???????K85mdmonitor ??????S07iscsid ???????S13rpcbind ??S23NetworkManager ?S26udev-post ?S84ksm ???????S91smbK25sshd ??????K69rpcsvcgssd ?K89netplugd ???????S08ip6tables ????S14nfslock ??S24portreserve ???S30vboxdrv ???S85gpm ???????S99alsasound这个级别nfs服务是开启的，被成为完全多用户模式。?init 4[root@localhost ~ ]# ls /etc/rc.d/rc4.d/K01dnsmasq ???K30sendmail ???K66gpsd ???????????K85mdmonitor ????S07iscsid ????S13rpcbind ???S23NetworkManager ?S26udev-post ?S84ksm ???????S99localK10saslauthd ?K35nmb ????????K69rpcsvcgssd ?????K89netplugd ?????S08ip6tables ?S14nfslock ???S24portreserve ????S30vboxdrv ???S85gpmK10xfs ???????K35smb ????????K74lm_sensors ?????K89rdisc ????????S08iptables ??S18rpcidmapd ?S25cups ???????????S35qemu ??????S85ksmtunedK20nfs ???????K36mysqld ?????K76openvpn ????????K90network ??????S12rsyslog ???S19rpcgssd ???S25netfs ??????????S50bluetooth ?S90crondK25sshd ??????K50netconsole ?K84wpa_supplicant ?K99lvm2-monitor ?S13iscsi ?????S22messagebus ?S26acpid ??????????S50haldaemon ?S99alsasound?此模式被称为安全模式。?init 5[root@localhost ~ ]# ls /etc/rc.d/rc5.d/K01dnsmasq ???K25sshd ???????K66gpsd ????????K84wpa_supplicant ?K87rpcbind ??K90network ?????S22messagebus ?????S26udev-post ?S84ksm ???????S99localK10saslauthd ?K30sendmail ???K69rpcsvcgssd ??K85mdmonitor ??????K88iscsi ????K99lvm2-monitor ?S23NetworkManager ?S30vboxdrv ???S85ksmtunedK10xfs ???????K36mysqld ?????K74lm_sensors ??K85rpcgssd ????????K89iscsid ???S08ip6tables ???S25cups ???????????S35qemu ??????S91nmbK15gpm ???????K50netconsole ?K76openvpn ?????K85rpcidmapd ??????K89netplugd ?S08iptables ?????S25netfs ??????????S50bluetooth ?S91smbK20nfs ???????K60crond ??????K83portreserve ?K86nfslock ????????K89rdisc ????S12rsyslog ?????S26acpid ??????????S50haldaemon ?S99alsasound完整的图形模式?init 6[root@localhost ~ ]# ls /etc/rc.d/rc6.d/K01dnsmasq ???K15ksmtuned ?K35nmb ????????K60crond ??????K74lm_sensors ?K83portreserve ???K85rpcgssd ???K88iscsi ????K90network ??????S00killallK10cups ??????K16ksm ??????K35smb ????????K66gpsd ???????K75netfs ??????K84NetworkManager ?K85rpcidmapd ?K88rsyslog ??K92ip6tables ????S01rebootK10saslauthd ?K20nfs ??????K36mysqld ?????K69rpcsvcgssd ?K75udev-post ??K84wpa_supplicant ?K86nfslock ???K89iscsid ???K92iptablesK10xfs ???????K25sshd ?????K50haldaemon ??K70vboxdrv ????K76openvpn ????K85mdmonitor ?????K87alsasound ?K89netplugd ?K98qemuK15gpm ???????K30sendmail ?K50netconsole ?K74acpid ??????K83bluetooth ??K85messagebus ?????K87rpcbind ???K89rdisc ????K99lvm2-mo
