NAME
rwhod — system status server
SYNOPSIS
/usr/sbin/rwhod
[-s]
[-r]
DESCRIPTION
rwhod
is the server that maintains the database used by
rwho
and
ruptime
(see
rwho(1)
and
ruptime(1)).
rwhod
sends status information to and receives status information from
other nodes on the local network that are running
rwhod.
rwhod
is started at system boot time if the RWHOD variable
is set to 1 in the file
/etc/rc.config.d/netdaemons.
As an information sender,
it periodically queries the state of the system
and constructs status messages that are broadcast on a network.
As an information receiver, it listens for other
rwhod
servers' status messages, validates them,
then records them in a collection of files located in the
/var/spool/rwho
directory.
By default,
rwhod
both sends and receives information.
rwhod
also supports the following options:
- -s
Configures server to be an information sender only.
- -r
Configures server to be an information receiver only.
Status messages are generated approximately once every three minutes.
rwhod
transmits and receives messages at the port indicated in the
who
service specification (see
services(4)).
The messages sent and received, 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 before transmission.
System load averages are calculated from the number of jobs
in the run queue over the last 1-, 5- and 15-minute intervals.
The host name included is the one returned by the
gethostname()
system call (see
gethostname(2)).
The array at the end of the message
contains information about the users logged in
on the sending machine.
This information includes the contents of the
utmp
entry for each non-idle terminal line
and a value indicating the time
since a character was last received on the terminal line (see
utmp(4)).
rwhod
discards received messages if they did
not
originate at a
rwho
server's port, or if the host's name, as specified in the message,
contains any unprintable
ASCII
characters.
Valid messages received by
rwhod
are placed in files named
whod.hostname
in the
/var/spool/rwho
directory.
These files contain only the most recent message
in the format described above.
WARNINGS
rwhod
does not relay status information between networks.
Users often incorrectly interpret the server dying
as a machine going down.
AUTHOR
rwhod
was developed by the University of California, Berkeley.
FILES
- /var/spool/rwho/whod.*
Information about other machines.
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