On AIX, the System Resource Controller (SRC) is used to control subsystems and subservers. Every AIX administrator is surely familiar with the lssrc, startsrc and stopsrc commands. The chrctcp command, which is used to manage subsystems that are started via /etc/rc.tcpip, is not quite as well known. By using this command, editing the start script /etc/rc.tcpip can be avoided. Most administrators only know and use the “-a” (add/activate), “-d” (delete/deactivate) and “-S” (start, stop or restart subsystem) options. However, the chrctcp command offers even more functionality via the options “-c” (change) and “-s” (show), which SMIT also uses. (After all, chrctcp was probably written specifically for use by SMIT.)
A number of subsystems are started at boot time via /etc/rc.tcpip. However, only if there is an entry of the following form in the /etc/rc.tcpip script:
start /usr/sbin/inetd "$src_running"
If a specific subsystem is not to be started at boot time, the relevant subsystem must be commented out in /etc/rc.tcpip:
#start /usr/sbin/inetd "$src_running"
In principle, the change can be made with an editor. However, there is a much more elegant way using the chrctcp command. If a specific service should not be started at next boot, chrctcp can be used with the “-d” option to comment out the service:
# chrctcp -d inetd
# grep /usr/sbin/inet /etc/rc.tcpip
#start /usr/sbin/inetd "$src_running"
#
This has no effect on the currently running subsystem. If you also want to stop the running subsystem, you can either use the “stopsrc –s” command or, which is much easier, simply use the “-S” option of chrctcp:
# chrctcp -S -d inetd
0513-044 The /usr/sbin/inetd Subsystem was requested to stop.
#
The subsystem is commented out in /etc/rc.tcpip and an eventually running subsystem is stopped as well.
You can proceed in a similar way if you want to use a previously unused service from /etc/rc.tcpip. The “-a” option can be used to activate the corresponding entry:
# grep /usr/sbin/inetd /etc/rc.tcpip
#start /usr/sbin/inetd "$src_running"
# chrctcp -a inetd
# grep /usr/sbin/inetd /etc/rc.tcpip
start /usr/sbin/inetd "$src_running"
#
Note: The entry ‘#start /usr/sbin/inetd “$src_running”‘ must already be present and at the correct place in the file!
If not only the file /etc/rc.tcpip is to be adjusted, but the service is also to be started immediately, the “-S” option can be used again:
# grep /usr/sbin/inetd /etc/rc.tcpip
#start /usr/sbin/inetd "$src_running"
# chrctcp -S -a inetd
0513-059 The inetd Subsystem has been started. Subsystem PID is 5636582.
# grep /usr/sbin/inetd /etc/rc.tcpip
start /usr/sbin/inetd "$src_running"
#
In the following we will stick to inetd as an example. However, everything described applies in the same way to other subsystems.
Services such as inetd, syslogd, and others often have options and arguments that can be specified at startup. For example, inetd offers the following options and arguments:
-d Send debugging information to syslogd
-6 IPv6 support
file Specification of a configuration file to be used instead of /etc/inetd.conf.
The options and arguments used can be displayed with the chrctcp command and the “-s” option:
# chrctcp -s inetd
#debug_mode:ipv6_mode:config_file
no:no:
#
The sample output shows debugging and IPv6 disabled and no alternate configuration file specified.
With the option “-c” (change) you can change the options and arguments. Attributes can be specified with the “-f” option. As an example, let’s enable debugging and allow IPv6:
# chrctcp -c inetd -f debug=yes -f ipv6=yes
# grep /usr/sbin/inetd /etc/rc.tcpip
start /usr/sbin/inetd "$src_running" " -d -6 "
#
A look at /etc/rc.tcpip shows that the start of inetd has been supplemented with the options “-d” (debugging) and “-6” (IPv6)! Again, only the start file /etc/rc.tcpip has been changed, an inetd that may already be running remains unaffected by the change:
# ps -ef|grep ine[t]d
root 5636582 4587924 0 18:34:47 - 0:00 /usr/sbin/inetd
#
As with enabling and disabling subsystems, the “-S” option can also be used when changing:
# chrctcp -S -c inetd -f debug=yes -f ipv6=yes
0513-044 The inetd Subsystem was requested to stop.
0513-059 The inetd Subsystem has been started. Subsystem PID is 5636584.
#
The service is then stopped and restarted immediately. Then of course with the changed options and arguments:
# ps -ef|grep ine[t]d
root 5636584 4587924 0 18:49:25 - 0:00 /usr/sbin/inetd -d -6
#
The options and arguments used at next boot can be listed with the “-s” option:
# chrctcp -s inetd
#debug_mode:ipv6_mode:config_file
yes:yes:
#
A bit unfortunate is the fact that the names shown in the header (debug_mode, ipv6_mode, config_file) do not quite match the attribute names to be used. The correct supported attribute names in the case of inetd are debug, ipv6 and file.
In one of the next posts we will list the supported attributes for further subsystems and make them available in a table.
