NAME
rwhod —
system status server
SYNOPSIS
rwhod |
[-d] |
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.
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 options are as follows:
-d- Turn on debug mode.
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 gethostname(3) 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 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
/var/rwho. These files contain only the most recent
message, in the format described above.
Status messages are generated approximately once every 3 minutes.
SEE ALSO
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.