NAME
rwhod —
system status server
SYNOPSIS
rwhod |
[-i
interval]
[-u
user] |
DESCRIPTION
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 messages
on a network.
The following options are available:
-
-
- -i
interval
- Allows for the broadcast interval to be changed from the
default 3 minutes. The interval argument is the
number of seconds to change the interval to, or if the value is suffixed
by “m” then it is interpreted as minutes. The maximum allowed
value for the broadcast interval is 11 minutes because higher values will
cause ruptime(1) to mark
the host as being down.
-
-
- -u
user
- Drop privileges and become the user
user.
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 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
/var/rwho.
The server transmits and receives messages at the port indicated in the
“who” service specification; see
services(5). The messages sent
and received, are of the form:
struct outmp {
char out_line[8]; /* tty name */
char out_name[8]; /* user id */
int32_t out_time; /* time on */
};
struct whod {
char wd_vers;
char wd_type;
char wd_fill[2];
int32_t wd_sendtime;
int32_t wd_recvtime;
char wd_hostname[32];
int32_t wd_loadav[3];
int32_t wd_boottime;
struct whoent {
struct outmp we_utmp;
int32_t 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 5, 10, and 15 minute intervals prior to a server's
transmission; they are multiplied by 100 for representation in an integer. The
host name included is that returned by the
gethostname(3) function
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(5) 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(1)
server are discarded unless they originated at an
rwho(1) 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
/var/rwho.
These files contain only the most recent message, in the format described
above.
Status messages are generated by default approximately once every 3 minutes.
SEE ALSO
ruptime(1),
rwho(1)
HISTORY
The
rwhod command appeared in
4.2BSD.
BUGS
There should be a way to relay status information between networks. 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.