RWHOD(8)
NAME
rwhod − system status server
USAGE
/etc/rwhod
DESCRIPTION
Rwhod is the server which maintains the database used by the rwho(1) and ruptime(1) programs. Its operation is predicated on the ability to broadcast messages on a network.
Rwhod both produces and consumes system status information. It periodically queries the state of the system and constructs status messages which are broadcast on a network, and it listens for other rwhod servers’ status messages as well. When it receives a status message from another server, rwhod validates it and records it in a file located in the directory /usr/spool/rwho.
The rwho server transmits and receives messages at the port indicated in the “rwho” service specification. 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 before transmission. The load averages represent 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 an 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 /usr/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(3) on /vmunix every 10 minutes to guard against the possibility that this file is not the system image currently operating.
NOTES
Rwhod does not relay status information between networks. Consequently, people often interpret the server’s dying as a machine in the network going down.