Examine INIT services -- Linux

Basic

Runlevel
        Runlevels may vary from OS to OS, but there're still some rules for them.
        Standard Runlevels
        0       JNB                     Shuts down the system
        S       Single-User Mode        Does not configure network interfaces or start daemons
        6       Reboot                  Reboots the system
        LSB specifications
        0       Halt                            Shuts down the system
        1       Single-User Mode                Mode for administrative tasks
        2       Multi-User Mode                 Does not configure network and does not export network services
        3       Multi-User Mode with Networking Starts the system Normally
        4       Not used/User-definable         For special purpose
        5       Normal Start with a GUI         runlevel 3 + display manager
        6       Reboot                          Reboots the system

Files in rc${runlevel}.d have names like K[0-9][0-9]* and S[0-9][0-9]*, is this a naming rule?
Do the names have implications?
The answer for both are YES.

rc stands for 'runtime configuration'.
The name rule is <K or S><priority><service>.
K stands for 'Kill', which means this service should be killed once the system enters this runlevel.
S stands for 'Start', which means this service should be started once the system enters this runlevel.
The lower the priority number, the higher the priority.
An experience formula: priority-with-S + priority-with-K = 100

Code

#!/usr/bin/env python

# This program examines services under /etc/rc<Runlevel>.d
# and generate a summary report.
class Service:
    def __init__(self, name):
        self.name = name
        self.start_rl_list = []
        self.stop_rl_list = []
    def getName(self):
        return self.name
    def addStartRL(self, rl):
        self.start_rl_list.append(rl)
        return
    def addStopRL(self, rl):
        self.stop_rl_list.append(rl)
        return
    def show(self):
        print '<%s>' % self.name
        print 'Start: ', self.start_rl_list
        print 'Stop: ', self.stop_rl_list
        print
        return
    
import re
import sys, os

dirpath_pattern = re.compile('/etc/rc([0-6S]).d')
service_pattern = re.compile('([KS])[0-9][0-9](.*)')

service_list = []
def alter_service_list(service_list, service_name, runlevel, action):
    for s in service_list:
        if s.getName() == service_name:
            if action == 'S':
                s.addStartRL(runlevel)
            else:
                s.addStopRL(runlevel)
            return
    service = Service(service_name)
    if action == 'S':
        service.addStartRL(runlevel)
    else:
        service.addStopRL(runlevel)
    service_list.append(service)
    return

# traverse /etc, for every dir matching dirname_pattern
# examine every file in it, if file name matches service_pattern
# then extract its behavior group(1) and its name group(2)
# operate on the service list
DIRECTORY = '/etc'
for dirpath, dirnames, filenames in os.walk(DIRECTORY):
    match = dirpath_pattern.match(dirpath)
    if match:
        runlevel = match.group(1)
        for f in filenames:
            match = service_pattern.match(f)
            if match:
                action = match.group(1)
                service_name = match.group(2)
                alter_service_list(service_list, service_name, runlevel, action)

for s in service_list:
    s.show()

Result

chenqi@chenqi-OptiPlex-760:~/mypro/python/examine-service$ ./examine_service.py | awk 'BEGIN { FS="\n"; RS=""; OFS="\t\t\t\t" } { print $1, $2, $3 }'
<pulseaudio>                Start:  ['5', '2', '3', '4']                Stop:  ['1']
<saned>                Start:  ['5', '2', '3', '4']                Stop:  ['1']
<killprocs>                Start:  ['1']                Stop:  []
<acpi-support>                Start:  ['5', '2', '3', '4']                Stop:  ['1']
<apache2>                Start:  ['5', '2', '3', '4']                Stop:  ['1', '0', '6']
<dns-clean>                Start:  ['1', '5', '2', '3', '4']                Stop:  []
<speech-dispatcher>                Start:  ['5', '2', '3', '4']                Stop:  ['1', '0', '6']
<single>                Start:  ['1']                Stop:  []
<pppd-dns>                Start:  ['1', '5', '2', '3', '4']                Stop:  []
<kerneloops>                Start:  ['5', '2', '3', '4']                Stop:  ['1']
<grub-common>                Start:  ['5', '2', '3', '4']                Stop:  []
<ondemand>                Start:  ['5', '2', '3', '4']                Stop:  []
<rc.local>                Start:  ['5', '2', '3', '4']                Stop:  []
<sudo>                Start:  ['5', '2', '3', '4']                Stop:  []
<rsync>                Start:  ['5', '2', '3', '4']                Stop:  []
<apparmor>                Start:  ['S']                Stop:  []
<setserial>                Start:  ['S']                Stop:  ['0', '6']
<x11-common>                Start:  ['S']                Stop:  []
<etc-setserial>                Start:  ['S']                Stop:  ['0', '6']
<brltty>                Start:  ['S']                Stop:  []
<urandom>                Start:  ['S', '0', '6']                Stop:  []
<halt>                Start:  ['0']                Stop:  []
<umountnfs.sh>                Start:  ['0', '6']                Stop:  []
<sendsigs>                Start:  ['0', '6']                Stop:  []
<umountfs>                Start:  ['0', '6']                Stop:  []
<umountroot>                Start:  ['0', '6']                Stop:  []
<networking>                Start:  ['0', '6']                Stop:  []
<unattended-upgrades>                Start:  []                Stop:  ['0', '6']
<reboot>                Start:  ['6']                Stop:  []

chenqi@chenqi-OptiPlex-760:~/mypro/python/examine-service$ ./examine_service.py | awk 'BEGIN { FS="\n"; RS=""; OFS="\t\t\t\t" } { print $1, $2, $3 }' | grep apache
<apache2>                Start:  ['5', '2', '3', '4']                Stop:  ['1', '0', '6']