Subsystem Resource Controller (SRC)

Objectives

  •  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.

Subsystem 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.

SubSystem:
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
2) lssrc -s
3) lssrc -g
4) lssrc -p 4) startsrc -g
5) stopsrc -g
6) startsrc -s
7) stopsrc -s
8) startsrc -t
9) stopsrc -t
10) refresh <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

Example:

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

Flag(s) Description
-s Name of the new subsystem
-p Full path to executable program / shell script.
-u Numeric uid for subsystem execution.   Must be a defined user.
Optional information:
-i, -o, -e Standard input, output, error devices.     Default is /dev/console
-a Arguments to the executable.
-G 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.
-E “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.
-w Wait time between a normal and forced stop.
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