Linux之runlevel

[root@localhost run]# cat /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).
#
<strong># 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)</strong>
# 
<strong>id:5:initdefault:</strong>

在一个运行的Linux系统中，可以通过如下一些方法知道当前的runlevel。

[root@localhost etc]# <strong>runlevel</strong>
N 5
[root@localhost etc]# 
[root@localhost etc]# which runlevel
/sbin/runlevel
[root@localhost etc]# 
[root@localhost etc]# file /sbin/runlevel
/sbin/runlevel: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, stripped
[root@localhost etc]# 
[root@localhost etc]# 
[root@localhost etc]# 
[root@localhost etc]# <strong>who -r</strong>
         run-level 5  2013-09-03 13:57
[root@localhost etc]# 
[root@localhost etc]#

runlevel命令是一个二进制文件，并非脚本。

也有人说可以使用如下两个环境变量进行查找，但是，需要系统支持。

$ echo $RUNLEVEL
$ echo $PREVLEVEL

Linux下的service也有runlevel，可以控制不同的service在不同的runlevel下的状态。

[root@localhost etc]# chkconfig --list
NetworkManager 	0:off	1:off	2:off	3:off	4:off	5:off	6:off
abrtd          	0:off	1:off	2:off	3:on	4:off	5:on	6:off
acpid          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
atd            	0:off	1:off	2:off	3:on	4:on	5:on	6:off
auditd         	0:off	1:off	2:on	3:on	4:on	5:on	6:off
autofs         	0:off	1:off	2:off	3:on	4:on	5:on	6:off
avahi-daemon   	0:off	1:off	2:off	3:on	4:on	5:on	6:off
bluetooth      	0:off	1:off	2:off	3:on	4:on	5:on	6:off
certmonger     	0:off	1:off	2:off	3:off	4:off	5:off	6:off
cgconfig       	0:off	1:off	2:on	3:on	4:on	5:on	6:off
cgred          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
cpuspeed       	0:off	1:on	2:on	3:on	4:on	5:on	6:off
crond          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
cups           	0:off	1:off	2:on	3:on	4:on	5:on	6:off
dnsmasq        	0:off	1:off	2:off	3:off	4:off	5:off	6:off
dovecot        	0:off	1:off	2:off	3:off	4:off	5:off	6:off
firstboot      	0:off	1:off	2:off	3:off	4:off	5:off	6:off
haldaemon      	0:off	1:off	2:off	3:on	4:on	5:on	6:off
httpd          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
ip6tables      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
iptables       	0:off	1:off	2:on	3:on	4:on	5:on	6:off
irqbalance     	0:off	1:off	2:off	3:on	4:on	5:on	6:off
iscsi          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
iscsid         	0:off	1:off	2:off	3:on	4:on	5:on	6:off
kdump          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
libvirt-guests 	0:off	1:off	2:off	3:on	4:on	5:on	6:off
libvirtd       	0:off	1:off	2:off	3:on	4:on	5:on	6:off
lvm2-monitor   	0:off	1:on	2:on	3:on	4:on	5:on	6:off
mdmonitor      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
messagebus     	0:off	1:off	2:on	3:on	4:on	5:on	6:off
mysqld         	0:off	1:off	2:on	3:on	4:on	5:on	6:off
netconsole     	0:off	1:off	2:off	3:off	4:off	5:off	6:off
netfs          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
network        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
nfs            	0:off	1:off	2:off	3:off	4:off	5:off	6:off
nfslock        	0:off	1:off	2:off	3:on	4:on	5:on	6:off
nscd           	0:off	1:off	2:off	3:off	4:off	5:off	6:off
nslcd          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
ntpd           	0:off	1:off	2:off	3:off	4:off	5:off	6:off
ntpdate        	0:off	1:off	2:off	3:off	4:off	5:off	6:off
oddjobd        	0:off	1:off	2:off	3:off	4:off	5:off	6:off
portreserve    	0:off	1:off	2:on	3:on	4:on	5:on	6:off
postfix        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
psacct         	0:off	1:off	2:off	3:off	4:off	5:off	6:off
qpidd          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
rdisc          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
restorecond    	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rhnsd          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
rpcbind        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
rpcgssd        	0:off	1:off	2:off	3:on	4:on	5:on	6:off
rpcidmapd      	0:off	1:off	2:off	3:on	4:on	5:on	6:off
rpcsvcgssd     	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rsyslog        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
saslauthd      	0:off	1:off	2:off	3:off	4:off	5:off	6:off
smartd         	0:off	1:off	2:off	3:off	4:off	5:off	6:off
snmpd          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
snmptrapd      	0:off	1:off	2:off	3:off	4:off	5:off	6:off
spamassassin   	0:off	1:off	2:off	3:off	4:off	5:off	6:off
sshd           	0:off	1:off	2:on	3:on	4:on	5:on	6:off
sssd           	0:off	1:off	2:off	3:off	4:off	5:off	6:off
sysstat        	0:off	1:on	2:on	3:on	4:on	5:on	6:off
tgtd           	0:off	1:off	2:off	3:off	4:off	5:off	6:off
tomcat6        	0:off	1:off	2:off	3:off	4:off	5:off	6:off
udev-post      	0:off	1:on	2:on	3:on	4:on	5:on	6:off
vncserver      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
vsftpd         	0:off	1:off	2:off	3:off	4:off	5:off	6:off
wpa_supplicant 	0:off	1:off	2:off	3:off	4:off	5:off	6:off
xinetd         	0:off	1:off	2:off	3:on	4:on	5:on	6:off
ypbind         	0:off	1:off	2:off	3:off	4:off	5:off	6:off

xinetd based services:
	amanda:        	off
	chargen-dgram: 	off
	chargen-stream:	off
	cvs:           	off
	daytime-dgram: 	off
	daytime-stream:	off
	discard-dgram: 	off
	discard-stream:	off
	echo-dgram:    	off
	echo-stream:   	off
	rsync:         	off
	tcpmux-server: 	off
	telnet:        	on
	time-dgram:    	off
	time-stream:   	off
[root@localhost etc]#