IN.RWHOD(8) Maintenance 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)