Tuesday, 27 November 2012

Lesson 2 - System Resource Controller

System Resource Controller (SRC)


Purpose of SRC
Parts of  SRC
Commands involved in SRC

 Purpose of SRC

  • A set of commands that make it very easy for the system administrators to maintain and manage the subsystems and subservers running on the system. 
  •  The subsystems and subservers are commonly called as “daemons”. 
  •  SRC allows us to stop, start, trace, list and refresh daemons. 
  •  SRC is started during the system initialization with a record for /usr/bin/srcmstr  daemon in the /etc/inittab file. 
  •  If the “srcmstr” daemon stops abnormally, the respawn action specified in /etc/inittab restarts the daemon .

 SRC hierarchy example

Fig: SRC Hierarchy

Components of SRC

There are 3 important components in the SRC

                   Subgroup  --> SubSystem --> SubServer

SubServer :
          A  subserver is a program or process that belongs to a subsystems, usually called daemons.
          Ex:  ftpd, telnetd are good examples of subservers.

          A “subsystem” is a program or process ( a group of program or process) that perform related functions .  Subsystems can be further divided into subservers.
          Ex: inetd, gated, routed, named etc.,

Subsystem Group:
          A group of any specified subsystems. Grouping subsystems together allows the control of several subsystems at one time. 

        Ex: TCP/IP, NIS, NFS , spooler 

          #lssrc -g spooler     
        subsystem Group PID Status
          qdaemon    spooler 8022 active
          writesrv     spooler 9558 active
          lpd           spooler inoperative

        The following derives the relationship between subsystem/subservers  and subsystem group that are taken care by SRC

         #lssrc -a

General Commands

                1)  lssrc -t <subserver>
                2)  lssrc -s <subsystem>
                3)  lssrc -g <subsystem group>
                4) lssrc -p <PID>
                4) startsrc -g <ss group>
                5) stopsrc -g <ss group>
                6) startsrc -s <subsystem>
                7) stopsrc -s <subsystem>
                8) startsrc -t <subserver>
                9) stopsrc -t <subserver>
10) refresh <-g> <-s> <-t> <sg,ss,srvs>
11) mkssys  --> To add subsystem
12) rmssys -s < SS>  --> To remove the subsystem
13) chssys    --> Change the subsystem attributes

Create your own SRC subsystem

Using  “mkssys” command to register the  your new subsystem under the control of SRC

Common mkssys command options

Name of the new subsystem
Full path to executable program / shell script.
Numeric uid for subsystem execution.   Must be a defined user.

Optional information:
-i, -o, -e
Standard input, output, error devices.     Default is /dev/console
Arguments to the executable.
Group name for related subsystems.
-K, -S, -I
Method of communications (Sockets [-K], Signals [-S], or Messages [-I]).     Default is Sockets.
-n, -f
The signal numbers used for normal (-n), or forced (-f), subsystem stop, if signals are used for communications.
“Nice” value for subsystem execution priority.
-R, -O
Automatic restart (-R), or abort (-O) on abnormal termination. Whether to respawn or not.
-Q, -q
Single (-Q), or multiple (-q) instances allowed.
Wait time between a normal and forced stop.


#mkssys  -s example -p /usr/local/sample/script.sh -u $(uid -u user)  -S -n 15 -f 9 -R -Q

How to add inetd services?

i)   Add the appropriate port information to /etc/services file
ii) Add the appropriate configuration information to /etc/inetd.conf file
iii)   #refresh -s inetd


  1. If you want your ex-girlfriend or ex-boyfriend to come crawling back to you on their knees (even if they're dating somebody else now) you have to watch this video
    right away...

    (VIDEO) Why your ex will NEVER come back...

  2. Quantum Binary Signals

    Professional trading signals sent to your mobile phone every day.

    Follow our signals NOW & earn up to 270% a day.

  3. BlueHost is the best hosting company for any hosting services you might need.