rwhod.tproj/rwhod.8

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  32 .\"     @(#)rwhod.8     8.2 (Berkeley) 12/11/93
  33 .\"
  34 .Dd December 11, 1993
  35 .Dt RWHOD 8
  36 .Os BSD 4.2
  37 .Sh NAME
  38 .Nm rwhod
  39 .Nd system status server
  40 .Sh SYNOPSIS
  41 .Nm rwhod
  42 .Sh DESCRIPTION
  43 .Nm Rwhod
  44 is the server which maintains the database used by the
  45 .Xr rwho 1
  46 and
  47 .Xr ruptime 1
  48 programs.  Its operation is predicated on the ability to
  49 .Em broadcast
  50 messages on a network.
  51 .Pp
  52 .Nm Rwhod
  53 operates as both a producer and consumer of status information.
  54 As a producer of information it periodically
  55 queries the state of the system and constructs
  56 status messages which are broadcast on a network.
  57 As a consumer of information, it listens for other
  58 .Nm rwhod
  59 servers' status messages, validating them, then recording
  60 them in a collection of files located in the directory
  61 .Pa /var/rwho .
  62 .Pp
  63 The server transmits and receives messages at the port indicated
  64 in the ``rwho'' service specification; see
  65 .Xr services 5 .
  66 The messages sent and received, are of the form:
  67 .Bd -literal -offset indent
  68 struct  outmp {
  69         char    out_line[8];            /* tty name */
  70         char    out_name[8];            /* user id */
  71         long    out_time;               /* time on */
  72 };
  73
  74 struct  whod {
  75         char    wd_vers;
  76         char    wd_type;
  77         char    wd_fill[2];
  78         int     wd_sendtime;
  79         int     wd_recvtime;
  80         char    wd_hostname[32];
  81         int     wd_loadav[3];
  82         int     wd_boottime;
  83         struct  whoent {
  84                 struct  outmp we_utmp;
  85                 int     we_idle;
  86         } wd_we[1024 / sizeof (struct whoent)];
  87 };
  88 .Ed
  89 .Pp
  90 All fields are converted to network byte order prior to
  91 transmission.  The load averages are as calculated by the
  92 .Xr w 1
  93 program, and represent load averages over the 5, 10, and 15 minute
  94 intervals prior to a server's transmission; they are multiplied by 100
  95 for representation in an integer.  The host name
  96 included is that returned by the
  97 .Xr gethostname 2
  98 system call, with any trailing domain name omitted.
  99 The array at the end of the message contains information about
 100 the users logged in to the sending machine.  This information
 101 includes the contents of the
 102 .Xr utmp 5
 103 entry for each non-idle terminal line and a value indicating the
 104 time in seconds since a character was last received on the terminal line.
 105 .Pp
 106 Messages received by the
 107 .Xr rwho
 108 server are discarded unless they originated at an
 109 .Xr rwho
 110 server's port.  In addition, if the host's name, as specified
 111 in the message, contains any unprintable
 112 .Tn ASCII
 113 characters, the
 114 message is discarded.  Valid messages received by
 115 .Nm rwhod
 116 are placed in files named
 117 .Pa whod.hostname
 118 in the directory
 119 .Pa /var/rwho .
 120 These files contain only the most recent message, in the
 121 format described above.
 122 .Pp
 123 Status messages are generated approximately once every
 124 3 minutes.
 125 .Nm Rwhod
 126 performs an
 127 .Xr nlist 3
 128 on
 129 .Pa /vmunix
 130 every 30 minutes to guard against
 131 the possibility that this file is not the system
 132 image currently operating.
 133 .Sh SEE ALSO
 134 .Xr rwho 1 ,
 135 .Xr ruptime 1
 136 .Sh BUGS
 137 There should be a way to relay status information between networks.
 138 Status information should be sent only upon request rather than continuously.
 139 People often interpret the server dying
 140 or network communication failures
 141 as a machine going down.
 142 .Sh HISTORY
 143 The
 144 .Nm
 145 command appeared in
 146 .Bx 4.2 .