IN.RWHOD(8) Maintenance Commands and Procedures IN.RWHOD(8)
NAME
in.rwhod, rwhod - system status server
SYNOPSIS
/usr/sbin/in.rwhod [
-m [
ttl]]
DESCRIPTION
in.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 or multicast messages on a network.
in.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
in.rwhod servers' status messages, validating
them, then recording them in a collection of files located in the
directory
/var/spool/rwho.
The
rwho server transmits and receives messages at the port indicated
in the
rwho service specification, see
services(5). The messages sent
and received are defined in
/usr/include/protocols/rwhod.h and are of
the 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 load averages are as calculated by the
w(1) program, and
represent load averages over the 1, 5, and 15 minute intervals prior
to a server's transmission. The host name included is that returned
by the
uname(2) system call. The array at the end of the message
contains information about the users who are logged in to the sending
machine. This information includes the contents of the
utmpx(5) 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
in.rwhod are placed in files named
whod.hostname in the directory
/var/spool/rwho. These files contain only the most recent message, in
the format described above.
Status messages are generated approximately once every 3 minutes.
OPTIONS
The following options are supported:
-m [
ttl ]
Use the rwho
IP multicast address (224.0.1.3) when
transmitting. Receive announcements both on this
multicast address and on the
IP broadcast address. If
ttl is not specified
in.rwhod multicasts on all
interfaces but with the
IP TimeToLive set to 1 (that
is, packets are not forwarded by multicast routers.) If
ttl is specified
in.rwhod only transmits packets on
one interface and setting the
IP TimeToLive to the
specified
ttl.
FILES
/var/spool/rwho/whod.* information about other machines
SEE ALSO
ruptime(1),
rwho(1),
w(1),
uname(2),
services(5),
utmpx(5),
attributes(7)WARNINGS
This service can cause network performance problems when used by
several hosts on the network. It is not run at most sites by default.
If used, include the
-m multicast option.
NOTES
This service takes up progressively more network bandwidth as the
number of hosts on the local net increases. For large networks, the
cost becomes prohibitive.
in.rwhod should relay status information between networks. People
often interpret the server dying as a machine going down.
December 8, 2001 IN.RWHOD(8)
