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Startup/Kill Scripts

 
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# 1  
Old 12-14-2009
Startup/Kill Scripts
Hello,

I have to perform an audit of a system at work and I am looking at its /etc/rc3.d:

Code:
K01tog-pegasus     K74nscd             S08iptables    S50openemm
K01yum             K74ntpd             S09isdn        S55cups
K02NetworkManager  K85mdmpd            S09pcmcia      S55sshd
K03rhnsd           K87auditd           S10network     S56rawdevices
K05saslauthd       K88wpa_supplicant   S12syslog      S56xinetd
K10dc_server       K89netplugd         S13irqbalance  S80sendmail
K10psacct          K89rdisc            S13portmap     S85gpm
K12dc_client       K90bluetooth        S14nfslock     S90crond
K15httpd           K94diskdump         S15mdmonitor   S93mysqld
K20nfs             K99readahead        S18rpcidmapd   S94httpd
K24irda            K99readahead_early  S19rpcgssd     S95anacron
K36mysqld          S00microcode_ctl    S25netfs       S95atd
K50netdump         S02lvm2-monitor     S26apmd        S97messagebus
K50tux             S05kudzu            S28autofs      S98haldaemon
K73ypbind          S05openibd          S40smartd      S99local
K74ipmi            S06cpuspeed         S44acpid       S99paNeuron

I notice that amost all the kill scripts do not have a corresponding start script and vice versa. Shouldn't a kill script have a corresponding start script and vice versa? Please explain.
# 2  
Old 12-14-2009
Typically you'll find that kill scripts are not run at the same run level as the start scripts.
You could check the output of:
Code:
ls -l /etc/rc?.d

# 3  
Old 12-14-2009
Quote:
Originally Posted by Scrutinizer
Typically you'll find that kill scripts are not run at the same run level as the start scripts.
You could check the output of:
Code:
ls -l /etc/rc?.d

I think am having problems understanding the basic idea begind the K and S scripts. Could someone explain to me how they work?

I found this on the internet:

Code:
The init command first stops all of the K symbolic links in the directory 
by issuing the /etc/rc.d/init.d/<command> stop command, where <command> 
is the process to be killed. It then starts all of the S symbolic links 
by issuing /etc/rc.d/init.d/<command> start.

After reading the above info I have this question:
Why would processes have to be killed if they have not been started in the first place?
# 4  
Old 12-14-2009
How should the system know in advance which services are running and which are not? Since it's possible to change runlevels in a running system (after all, that's what "shutdown" and "reboot" really do), and the services associated with each runlevel that would be quite non-trivial.
# 5  
Old 12-14-2009
Quote:
Originally Posted by mojoman
After reading the above info I have this question:
Why would processes have to be killed if they have not been started in the first place?
Because they will have been started at a different run level. When a run level is changed, processes that should not be running at that run level will have to be stopped.
# 6  
Old 12-14-2009
Another way to think of it is there is no harm in trying to kill something that may or may not be running.

It does point out a deficiency of init, though. A smarter "init" would know what is running and not waste time on unneeded kills.
Last edited by TonyLawrence; 12-14-2009 at 05:09 PM.. Reason: spelling
# 7  
Old 12-14-2009
Quote:
Originally Posted by TonyLawrence
Another way to think of it is there is no harm in trying to kill something that may or may not be running.

It does point out a deficiency of init, though. A smarter "init" would know what is running and not waste time on unneeded kills.
That's fair enough, but how smart would init have to be to see a K scripts and decide not to run it because it may not have started something like that earlier? Smilie
Last edited by Scott; 12-14-2009 at 05:22 PM..
 
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