RWHOD(8)

NAME
rwhod - system status server

SYNOPSIS
rwhod [-i interval] [-u user]

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.

The following options are available:

-i interval
    Allows for the broadcast interval to be changed from the default 3 minutes. The interval argument is the number of seconds to change the interval to, or if the value is suffixed by “m” then it is interpreted as minutes. The maximum allowed value for the broadcast interval is 11 minutes because higher values will cause ruptime(1) to mark the host as being down.

-u user
    Drop privileges and become the user user.

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/rwho.

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

    struct	outmp {
    	char	out_line[8];		/* tty name */
    	char	out_name[8];		/* user id */
    	int32_t	out_time;		/* time on */
    };
    struct	whod {
    	char	wd_vers;
    	char	wd_type;
    	char	wd_fill[2];
    	int32_t	wd_sendtime;
    	int32_t	wd_recvtime;
    	char	wd_hostname[32];
    	int32_t	wd_loadav[3];
    	int32_t	wd_boottime;
    	struct	whoent {
    		struct	outmp we_utmp;
    		int32_t	we_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(3) function 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(1) server are discarded unless they originated at an rwho(1) 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/rwho. These files contain only the most recent message, in the format described above.

Status messages are generated by default approximately once every 3 minutes.

SEE ALSO
ruptime(1), rwho(1)

HISTORY
The rwhod command appeared in 4.2BSD.

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 communication failures as a machine going down.