NAME

rwhod, in.rwhod − system status server

SYNOPSIS

/usr/etc/in.rwhod

AVAILABILITY

Due to its potential impact on network performance, this service is commented out of the /etc/rc system initialization script.  It is provided only for 4.3 BSD compatibility. 

This program is available with the Networking software installation option.  Refer to Installing SunOS 4.1 for information on how to install optional software. 

DESCRIPTION

rwhod is the server which maintains the database used by the rwho(1C) and ruptime(1C) programs.  Its operation is predicated on the ability to broadcast messages on a network. 

rwhod operates as both a producer and consumer of status information.  As a producer of information it periodically queries the state of the system and constructs status messages which are broadcast on a network.  As a consumer of information, it listens for other rwhod servers’ status messages, validating them, then recording them in a collection of files located in the directory /var/spool/rwho. 

The rwho server transmits and receives messages at the port indicated in the “rwho” service specification, see services(5).  The messages sent and received, are of the form:

structoutmp {

charout_line[8];/∗ tty name ∗/
charout_name[8];/∗ user id ∗/
longout_time;/∗ time on ∗/

};
structwhod {

charwd_vers;
charwd_type;
charwd_fill[2];
intwd_sendtime;
intwd_recvtime;
charwd_hostname[32];
intwd_loadav[3];
intwd_boottime;

structwhoent {
structoutmp we_utmp;
intwe_idle;

} wd_we[1024 / sizeof (struct whoent)];

};

All fields are converted to network byte order prior to transmission.  The load averages are as calculated by the w(1) program, and represent load averages over the 5, 10, and 15 minute intervals prior to a server’s transmission.  The host name included is that returned by the gethostname(2) system call.  The array at the end of the message contains information about the users logged in to the sending machine.  This information includes the contents of the utmp(5V) entry for each non-idle terminal line and a value indicating the time since a character was last received on the terminal line. 

Messages received by the rwho server are discarded unless they originated at a rwho server’s port.  In addition, if the host’s name, as specified in the message, contains any unprintable ASCII characters, the message is discarded.  Valid messages received by rwhod are placed in files named whod.hostname in the directory /var/spool/rwho.  These files contain only the most recent message, in the format described above. 

Status messages are generated approximately once every 60 seconds.  rwhod performs an nlist (3V) on /vmunix every 10 minutes to guard against the possibility that this file is not the system image currently operating. 

FILES

/etc/rc

/var/spool/rwho

SEE ALSO

rwho(1C), ruptime(1C), w(1), gethostname(2), nlist(3V), utmp(5V), syslogd(8)

DIAGNOSTICS

Status and diagnostic messages are logged to the appropriate system log using the syslogd(8) facility. 

BUGS

This service takes up progressively more network bandwidth as the number of hosts on the local net increases.  For large networks, the cost becomes prohibitive.  RPC-based services such as rup(1C) and rusers(1C) provide a similar function with greater efficiency. 

rwhod should relay status information between networks.  People often interpret the server dying as a machine going down. 

Sun Release 4.1  —  Last change: 17 December 1987