rwhod(1M)

Requires Optional ARPA Services Software

NAME

rwhod − system status server

SYNOPSIS

/etc/rwhod [−s] [−r]

DESCRIPTION

rwhod is the server that maintains the database used by the rwho(1) and ruptime(1) programs. rwhod sends status information to and receives status information from other nodes on the local network that are running rwhod.

rwhod is started at system boot time when the lines that invoke it are uncommented in the file /etc/netbsdsrc.

As an information sender, it periodically queries the state of the system and constructs status messages that are broadcast on a network.

As an information receiver, it listens for other rwhod servers’ status messages, validates them, then records them in a collection of files located in the /usr/spool/rwho directory.

By default, rwhod both sends and receives information. rwhod also supports the following options:

−s Configures server to be an information sender only.

−r Configures server to be an information receiver only.

Status messages are generated approximately once every three minutes. rwhod transmits and receives messages at the port indicated in the who service specification (see services(4)). 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. System load averages are calculated from the number of jobs in the run queue over the last 1-, 5- and 15-minute intervals. The host name included is the one returned by the gethostname(2) system call. The array at the end of the message contains information about the users logged into the sending machine. This information includes the contents of the utmp(7) entry for each non-idle terminal line and a value indicating the time since a character was last received on the terminal line.

rwhod discards received messages if they did not originate at a rwho server’s port or if the host’s name, as specified in the message, contains any unprintable ASCII characters.

Valid messages received by rwhod are placed in files named whod.hostname in the /usr/spool/rwho directory. These files contain only the most recent message in the format described above.

WARNINGS

rwhod does not relay status information between networks. Users often incorrectly interpret the server dying as a machine going down.

AUTHOR

rwhod was developed by the University of California, Berkeley.

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