1

Starting Network Services

Version A.01H3065S Module 7 Slides

2 © 1999 Hewlett-Packard Co.

H3065S A.01

Starting System and Network Services

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PDC chooses a boot disk.

ISL finds and loads the kernel.

Kernel calls /sbin/init.

Init calls /sbin/rc.

/sbin/rc starts system and network services.

NFSDNS

NTP

NetworkSubsystem

Kernel(vmunix)

Network Drivers

…

Memory

/

/stand /etc /sbin /usr

File System

vmunix

LANIC

1

23

init

4

/sbin/rc

rc1.d rc2.d rc3.d

Networkdaemons

1

2

3

4

3 © 1999 Hewlett-Packard Co.

H3065S A.01

Run Levels

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• init and /sbin/rc start and stop services in stages called run levels.• The system run level determines what services are available.• At boot, init progresses from run level 1 to 3, starting services.• At shutdown, init progresses from run level 3 to 0, killing services.

• Example: (Not all run levels and services shown)

Run Level Services Available

3 syncer, NFS, CDE

2 syncer, NFS

1 syncer

0

Sta

rtu

pS

hu

tdow

n

4 © 1999 Hewlett-Packard Co.

H3065S A.01

/sbin/rc*.d Directories

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• /sbin/rc*.d directories determine at which run levels services start and stop.• /sbin/rc runs S scripts to start services during system startup.• /sbin/rc runs K scripts to kill services during system shutdown.

K100dtlogin.rc

K900nfs.server

S340net

S430nfs.client

S500inetd

S660xntpd

/sbin

rc2.d

rc1.d

rc0.d

rc3.d

5 © 1999 Hewlett-Packard Co.

H3065S A.01

S/K Script Naming Convention

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/sbin/rc2.d/S730cron

Run Level

Type

Sequence Number

Service Name

6 © 1999 Hewlett-Packard Co.

H3065S A.01

/sbin/init.d/* Scripts

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/sbin

init.d rc2.drc1.d

cronK270cron S730cronlink link

• Every service started by /sbin/rc has an associated script in /sbin/init.d.• /sbin/init.d scripts contain code needed to actually start/kill services.• /sbin/rc*.d/* scripts are just symbolic links to /sbin/init.d scripts!

7 © 1999 Hewlett-Packard Co.

H3065S A.01

What’s in an init.d Script?

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case $1 in start_msg) echo “Start clock daemon” stop_msg) echo “Stop clock daemon” start) # Commands to start cron stop) # Commands to kill cronesac

• Scripts in /sbin/init.d accept a single argument.• Scripts do one of four things, depending on the argument value.• Sample init.d script (simplified):

/sbin/init.d/cron:

8 © 1999 Hewlett-Packard Co.

H3065S A.01

/etc/rc.config.d/* Files

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/etc/rc.config.d/cron

CRON=1 # Set control variable to 1 to enable # Set control variable to 0 to disable

/sbin/init.d/cron (simplified)

case $1 in start_msg) echo “Start clock daemon” stop_msg) echo “Stop clock daemon” start) if CRON=1 then start the cron daemon stop) if CRON=1 then kill the cron daemonesac

• You may wish to disable a service that’s not needed, or enable a new service.• Services may be enabled or disabled via control variables.• Control variables are defined in files under /etc/rc.config.d.• /sbin/init.d/ scripts source /etc/rc.config.d/* files to determine control variable values.

9 © 1999 Hewlett-Packard Co.

H3065S A.01

Pulling it All Together

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Pool of Startup/Shutdown Scripts Data Configuration Files

/etc/rc.config.d/sbin/init.drc Script

net

inetd

nfs.server

nis.client...

netconf

netdaemons

nfsconf

namesvrs...

/sbin/rc1.d

/sbin/rc2.d

/sbin/rc3.d

K500inetdK660net

K900nfsS340netS500inetd

S100nfs.server

start

stop

stop_msg

start_msg

10 © 1999 Hewlett-Packard Co.

H3065S A.01

Viewing Console Messages when Changing Run Levels

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init brings system to run level 2.

init calls /sbin/rc.

/sbin/rc executes /sbin/rc2.d/S* scripts with start_msg argument.

/sbin/rc executes /sbin/rc2.d/S*scripts with start argument

Transition to run level 2 complete.

Start clock daemon..................[ ]Start internet services daemon......[ ]Start NFS client subsystem..........[ ]

Start clock daemon..................[N/A]Start internet services daemon......[OK ]Start NFS client subsystem..........[OK ]

11 © 1999 Hewlett-Packard Co.

H3065S A.01

Creating Custom Start Scripts

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Cookbook Procedure

1. cd /sbin/init.d2. cp template scope_collect3. vi scope_collect a. Edit start_msg statement b. Edit stop_msg statement c. Edit start statement i. Change CONTROL_VARIABLE to SCOPE_COLLECT ii. Add command /opt/perf/bin/scope.start iii. Add command set_return d. Edit stop statement i. Change CONTROL_VARIABLE to SCOPE_COLLECT ii. Add command /opt/perf/bin/scope.stop iii. Add command set_return4. vi /etc/rc.config.d/scope_collect a. Add single line, SCOPE_COLLECT=15. ln -s /sbin/init.d/scope_collect /sbin/rc3.d/S900scope_collect6. ln -s /sbin/init.d/scope_collect /sbin/rc2.d/K100scope_collect