1RWHOD(8)                  BSD System Manager's Manual                 RWHOD(8)


4     rwhod — system status server


7     rwhod [-bpa] [-u user]


10     Rwhod is the server which maintains the database used by the rwho(1) and
11     ruptime(1) programs.  Its operation is predicated on the ability to
12     broadcast messages on a network.
14     Rwhod operates as both a producer and consumer of status information.  As
15     a producer of information it periodically queries the state of the system
16     and constructs status messages which are broadcast on a network.  As a
17     consumer of information, it listens for other rwhod servers' status mes‐
18     sages, validating them, then recording them in a collection of files
19     located in the directory /var/spool/rwho.
21     The server transmits and receives messages at the port indicated in the
22     ``rwho'' service specification; see services(5).
24     If the -b flag is supplied, only broadcast interfaces, such as ethernets,
25     will be used.  If the -p flag is supplied, only point-to-point interfaces
26     will be used. If the -a flag is supplied, or no flags are supplied, all
27     interfaces will be used.
29     If the -u flag is supplied, rwhod will run as the specified user instead
30     of as root.
32     The messages sent and received, are of the form:
34           struct  outmp {
35                   char    out_line[8];            /* tty name */
36                   char    out_name[8];            /* user id */
37                   long    out_time;               /* time on */
38           };
40           struct  whod {
41                   char    wd_vers;
42                   char    wd_type;
43                   char    wd_fill[2];
44                   int     wd_sendtime;
45                   int     wd_recvtime;
46                   char    wd_hostname[32];
47                   int     wd_loadav[3];
48                   int     wd_boottime;
49                   struct  whoent {
50                           struct  outmp we_utmp;
51                           int     we_idle;
52                   } wd_we[1024 / sizeof (struct whoent)];
53           };
55     All fields are converted to network byte order prior to transmission.
56     The load averages are as calculated by the w(1) program, and represent
57     load averages over the 5, 10, and 15 minute intervals prior to a server's
58     transmission; they are multiplied by 100 for representation in an inte‐
59     ger.  The host name included is that returned by the gethostname(2) sys‐
60     tem call, with any trailing domain name omitted.  The array at the end of
61     the message contains information about the users logged in to the sending
62     machine.  This information includes the contents of the utmp(5) entry for
63     each non-idle terminal line and a value indicating the time in seconds
64     since a character was last received on the terminal line.
66     Messages received by the rwho server are discarded unless they originated
67     at an rwho server's port.  In addition, if the host's name, as specified
68     in the message, contains any unprintable ASCII characters, the message is
69     discarded.  Valid messages received by rwhod are placed in files named
70     whod.hostname in the directory /var/spool/rwho.  These files contain only
71     the most recent message, in the format described above.
73     Status messages are generated approximately once every 3 minutes.  Rwhod
74     recomputes the system boot time every 30 minutes because on some (non-
75     Linux) systems it is not a totally reliable process.


78     rwho(1), ruptime(1)


81     There should be a way to relay status information between networks.  Peo‐
82     ple often interpret the server dying or network communtication failures
83     as a machine going down.


86     The rwhod command appeared in 4.2BSD.
88Linux NetKit (0.17)              May 13, 1997              Linux NetKit (0.17)