rwhod(8c)
NAME
rwhod − system status server
SYNTAX
/etc/rwhod [ −b ] [ −l ]
DESCRIPTION
The rwhod command is the server which maintains the database used by the rwho() and ruptime() programs. Its operation is predicated on the ability to broadcast messages on a network.
The rwhod command 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 /usr/spool/rwho.
The rwho server transmits and receives messages at the port indicated in the “rwho” service specification, see services(.). 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 prior to transmission. The load averages are as calculated by the w() program, and represent load averages over the 5, 10, and 15 minute intervals prior to a server’s transmission. The host name included is that returned by the gethostname() system call. 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() 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 rwhod are placed in files named "whod.hostname" in the directory /usr/spool/rwho. These files contain only the most recent message, in the format described above.
Status messages are generated approximately once every 60 seconds. The rwhod command performs an nlist() on /vmunix every 10 minutes to guard against the possibility that this file is not the system image currently operating.
OPTIONS
−bbroadcast only mode, sends outgoing rwho packets but ignores incoming ones.
−llisten only mode, collects incoming rwho packets from the network, but does not broadcast rwho data.
RESTRICTIONS
If a system exceeds 40 users logged in at once, the output of the ruptime() and rwho() commands will be incomplete. Users who login to a machine after that point will fail to appear in the output of the ruptime() and rwho() commands. This is due to the maximum size limit of an Ethernet packet, which is 1500 bytes, and the fact that the rwho daemon must broadcast its information in a single packet.