rwhod

system status daemon

Syntax:

rwhod

Description:

The rwhod daemon is the server that maintains the database used by the rwho and ruptime utilities. Its operation is based on the network's ability to transmit broadcast messages.

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

The daemon transmits and receives messages at the port indicated by the rwho entry in the services file. The messages are sent and received in this form:


struct  outmp {
        char out_line[8];    /* tty name */
        char out_name[8];    /* user id */
        long out_time;       /* time on */
};

struct  whod {
        char    wd_vers;
        char    wd_type;
        char    wd_fill[2];
        int     wd_sendtime;
        int     wd_recvtime;
        char    wd_hostname[32];
        int     wd_loadav[3];
        int     wd_boottime;
        struct  whoent {
                struct  outmp we_utmp;
                int     we_idle;
        } wd_we[1024 / sizeof (struct whoent)];
};

All fields are converted to network byte order prior to transmission. The hostname included is that returned by the gethostname() 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 a value indicating the time in seconds since a character was last received on the terminal line.

Messages received by the rwhod daemon are discarded unless they originated at an rwhod daemon'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.

The rwhod daemon generates status messages about every three minutes.

See also:

rwho, ruptime