NAME

rwhod − system status server

SYNOPSIS

/etc/rwhod

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 /usr/spool/rwho.

The 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; they are multiplied by 100 for representation in an integer.  The host name included is that returned by the gethostname(2) system call, with any trailing domain name omitted. 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(5) entry for each non-idle terminal line and a value indicating the time in seconds since a character was last received on the terminal line.

Messages received by the rwho server are discarded unless they originated at an 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 /usr/spool/rwho. These files contain only the most recent message, in the format described above.

Status messages are generated approximately once every 3 minutes. 

SEE ALSO

rwho(1C), ruptime(1C)

BUGS

There should be a way to relay status information between networks.  Status information should be sent only upon request rather than continuously.  People often interpret the server dying or network communtication failures as a machine going down. 

September 02, 1992