RWHOD(1M) RWHOD(1M)
rwhod - system status server
/usr/etc/rwhod [ -m [ ttl ] ]
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 or multicast messages on a network. Rwhod is started at system
initialization if the configuration flag rwhod is set ``on'' with
chkconfig(1M). Site-dependent options and arguments to rwhod belong in
the file /etc/config/rwhod.options.
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 or multicast 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(4). The messages sent and
received, are defined in <protocols/rwhod.h>:
struct outmp {
char out_line[8]; /* tty name */
char out_name[8]; /* user id */
long out_time; /* time on */
};
struct whod {
char wd_vers; /* protocol version # */
char wd_type; /* packet type: WHODTYPE_STATUS */
char wd_pad[2];
int wd_sendtime; /* time stamp by sender */
int wd_recvtime; /* time stamp applied by receiver */
char wd_hostname[32];/* host's name */
int wd_loadav[3];/* load average as in uptime */
int wd_boottime; /* time system booted */
struct whoent {
struct outmp we_utmp;/* active tty info */
int we_idle; /* tty idle time */
} wd_we[1024 / sizeof (struct whoent)];
};
All fields are converted to network byte order prior to transmission.
The load averages represent smoothed CPU loads over the 5, 10, and 15
minute intervals prior to a server's transmission; they are multiplied by
100 for representation in an integer.
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RWHOD(1M) RWHOD(1M)
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(4) 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. Rwhod
performs an nlist(3) on /unix every 30 minutes to guard against the
possibility that this file is not the system image currently operating.
Rhwod recognizes the following options:
-m causes rwhod to use IP multicast (instead of broadcast or unicast)
on all multicast-capable interfaces (excluding the loopback
interface). The multicast reports are sent with a time-to-live of
1, to prevent forwarding beyond the directly-connected subnet(s).
-m ttl
causes rwhod to send IP multicast datagrams with a time-to-live of
ttl, via the default multicast interface only rather than all
interfaces. ttl must be between 0 and 32. Note that "-m 1" is
different than "-m", in that "-m 1" specifies transmission on one
interface only. This allows the information to be relayed between
networks.
When "-m" is used without a ttl argument, the program accepts multicast
rwhod reports from all multicast-capable interfaces. If a ttl argument
is given, it accepts multicast reports from only one interface, the one
on which reports are sent (which may be controlled via the host's routing
table). Regardless of the "-m" option, the program accepts broadcast or
unicast reports from all interfaces. Thus, this program will hear the
reports of old, non-multicasting rwhod's, but, if multicasting is used,
those old rwhod's won't hear the reports generated by this program.
rwho(1C), ruptime(1C), rup(1C)
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.
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