rwhod Daemon

Purpose

Provides the server function for the rwho and ruptime commands.

Syntax

Note: Use SRC commands to control the rwhod daemon from the command line. Use the rc.tcpip file to start the daemon with each system startup.

/usr/sbin/rwhod

Description

The /usr/sbin/rwhod daemon maintains the database used by the rwho and ruptime commands. Once started, the rwhod daemon operates as both producer and consumer of status information.

As a producer of status information, the rwhod daemon queries the state of the local host approximately every 3 minutes. It then constructs status messages and broadcasts them to the local network.

As a consumer of status information, the rwhod daemon listens for status messages from rwhod servers on remote hosts. When the rwhod daemon receives a status message, it validates the received status message. It then records the message in the /var/spool/rwho directory. (The rwho and ruptime commands use the files in the /var/spool/rwho directory to generate their status listings.)

The rwhod daemon broadcasts and receives status messages using the rwho socket as specified in the /etc/services file.

When creating these messages, the rwhod daemon calculates the entries for the average CPU load for the previous 1-, 5-, and 15-minute intervals. Before broadcasting these messages, the rwhod daemon converts them to the byte order that the network can use.

When the rwhod daemon receives messages on the rwho socket, it discards any that do not originate from an rwho socket. Additionally, it discards any messages that contain unprintable ASCII characters. When the rwhod daemon receives a valid message, it places the message in a whod.HostName file in the /var/spool/rwho directory, overwriting any file with the same name.

The rwhod daemon should be controlled using the System Resource Controller (SRC). Entering rwhod at the command line is not recommended.

Manipulating the rwhod Daemon with the System Resource Controller

The rwhod daemon is a subsystem controlled by the System Resource Controller (SRC). The rwhod daemon is a member of the tcpip system group. This daemon is disabled by default and can be manipulated by the following SRC commands:

Examples

1. To start the rwhod daemon, enter the following:

   startsrc -s rwhod

   This command starts the daemon. You can use this command in the rc.tcpip file or on the command line. The -s flag specifies that the subsystem that follows is to be started.
2. To stop the rwhod daemon normally, enter the following:

   stopsrc -s rwhod

   This command stops the daemon. The -s flag specifies that the subsystem that follows is to be stopped.
3. To get a short status report from the rwhod daemon, enter the following:

   lssrc -s rwhod

   This command returns the name of the daemon, the process ID of the daemon, and the state of the daemon (active or inactive).
4. To enable tracing for rwhod daemon, enter the following:

   traceson -s rwhod

   This command enables socket level debugging. Use the trpt command to look at the output of this example command.

Files

Related Information

The ruptime command, rwho command, who command.

The gethostname subroutine.

The services file format.

TCP/IP Daemons in AIX Version 4.3 System Management Guide: Communications and Networks.