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System Administration Guide: Advanced Administration
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Port Monitor Service Administration (pmadm)

The pmadm command enables you to administer port monitors' services. In particular, you use the pmadm command to add or remove a service and to enable or disable a service. You can also install or replace per-service configuration scripts, or print information about a service.

Each instance of a service must be uniquely identified by a port monitor and a port. When you use the pmadm command to administer a service, you specify a particular port monitor with the pmtag argument, and a particular port with the svctag argument.

For each port monitor type, the SAF requires a specialized command to format port monitor-specific configuration data. This data is used by the pmadm command. For ttymon and listen type port monitors, these specialized commands are ttyadm and nlsadmin, respectively.

ttymon Port Monitor

Whenever you attempt to log in by using a directly connected modem or alphanumeric terminal, ttymon goes to work. First, the SAC process is started by SMF. Then, the SAC automatically starts the port monitors that are designated in its administrative file, /etc/saf/_sactab. After the ttymon port monitor has been started, it monitors the serial port lines for service requests.

When someone attempts to log in by using an alphanumeric terminal or a modem, the serial port driver passes the activity to the operating system. The ttymon port monitor notes the serial port activity, and attempts to establish a communications link. The ttymon port monitor determines which data transfer rate, line discipline, and handshaking protocol are required to communicate with the device.

After the proper parameters for communication with the modem or terminal are established, the ttymon port monitor passes these parameters to the login program and transfers control to it.

Port Initialization Process

When an instance of the ttymon port monitor is invoked by the SAC, ttymon starts to monitor its ports. For each port, the ttymon port monitor first initializes the line disciplines, if they are specified, and the speed and terminal settings. The values used for initialization are taken from the appropriate entry in the /etc/ttydefs file.

The ttymon port monitor then writes the prompt and waits for user input. If the user indicates that the speed is inappropriate by pressing the Break key, the ttymon port monitor tries the next speed and writes the prompt again.

If autobaud is enabled for a port, the ttymon port monitor tries to determine the baud rate on the port automatically. Users must press Return before the ttymon port monitor can recognize the baud rate and print the prompt.

When valid input is received, the ttymon port monitor does the following tasks:

  • Interprets the per-service configuration file for the port

  • Creates an /etc/utmpx entry, if required

  • Establishes the service environment

  • Invokes the service associated with the port

After the service terminates, the ttymon port monitor cleans up the /etc/utmpx entry, if this entry exists, and returns the port to its initial state.

Bidirectional Service

If a port is configured for bidirectional service, the ttymon port monitor does the following:

  • Allows users to connect to a service

  • Allows the uucico, cu, or ct commands to use the port for dialing out, if the port is free

  • Waits to read a character before printing a prompt

  • Invokes the port's associated service, without sending the prompt message, when a connection is requested, if the connect-on-carrier flag is set

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  Published under the terms fo the Public Documentation License Version 1.01. Design by Interspire