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, rwhod listens for the status messages of the other rwhod servers, 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. For more information, see services(.). The messages sent and received, take the following 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 calculated by the w() 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 as an integer. The host name included is the name returned by the gethostname() system 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() entry for each active 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.fIhostname in the directory /usr/spool/rwho. These files contain only the most recent message in the format previously described.
Status messages are generated approximately once every 3 minutes. The rwhod command performs an nlist() on /vmunix every 30 minutes to guard against the possibility that this file is not the system image currently operating.
Options
−bSets the broadcast only mode. Sends outgoing rwho packets, but ignores incoming ones.
−lSets the listen only mode. Collects incoming rwho packets from the network, but does not broadcast rwho data.
Restrictions
Because the rwhod daemon sends its information in broadcast packets it generates a large amount of network traffic. On large networks the extra traffic may be objectionable. Therefore, the rwhod daemon is disabled by default. To make use of the rwhod daemon for both the local and remote hosts, remove the comment symbols (#) from in front of the lines specifying rwhod in the /etc/rc file.
If the rwhod daemon is not running on a remote machine, the machine may incorrectly appear to be down when you use the ruptime command to determine its status. See the ruptime() reference page for more information.
If a system has more than 40 users logged in at once, the number of users displayed by the ruptime() and rwho() commands is incorrect. Users who login after the fortieth user, will fail to appear in the output of the ruptime() and rwho() commands. This is because the maximum size limit of an Ethernet packet is 1500 bytes, and the rwhod daemon must broadcast its information in a single packet.