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.