rwhod.8c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 8C 代码 · 共 161 行

.\" SCCSID: @(#)rwhod.8c	2.2	5/5/87
.TH rwhod 8c
.SH Name
rwhod \- system status server
.SH Syntax
.B "/etc/rwhod [ \-b ] [ \-l ]"
.SH Description
.NXR "rwhod server"
.NXR "system status server" "rwhod server"
.NXR "rwho command" "and the rwhod server"
.NXR "ruptime command" "and the rwhod server"
The
.PN rwhod
command is the server which maintains the database used by the 
.MS rwho 1c 
and 
.MS ruptime 1c 
programs.  Its operation is predicated on the ability to
broadcast messages on a network.
.PP
The
.PN 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.
.PP
As a consumer of information, 
.PN rwhod 
listens for the status messages of the other
.PN rwhod
servers, validating them, then recording
them in a collection of files located in the directory
.PN /usr/spool/rwho .
.PP
The
.PN rwho
server transmits and receives messages at the port indicated
in the rwho service specification. For more information, see 
.MS services 5 .
The messages sent and received, take the following form:
.NXR "rwhod server" "message format"
.EX
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)];
};
.EE
All fields are converted to network byte order prior to
transmission.  The load averages are calculated by the
.MS 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 as an integer.
The host name included is the name returned by the 
.MS gethostname 2 
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 
.MS utmp 5 
entry for each active terminal line and a value indicating the
time since a character was last received on the terminal line.
.PP
Messages received by the
.PN rwho
server are discarded unless they originated at a
.PN 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
.PN rwhod
are placed in files named 
\f(CWwhod.f\Ihostname\fR
in the directory 
.PN /usr/spool/rwho .
These files contain only the most recent message in the
format previously described.
.PP
Status messages are generated approximately once every
3 minutes.  
The
.PN rwhod
command performs an 
.MS nlist 3 
on 
.PN /vmunix 
every 30 minutes to guard against
the possibility that this file is not the system
image currently operating.
.SH Options
.IP \-b 5
Sets the broadcast only mode. Sends outgoing 
.PN rwho
packets, but ignores incoming ones.
.IP \-l
Sets the listen only mode. Collects incoming
.PN rwho
packets from the network, but does not broadcast
.PN rwho
data.
.SH Restrictions
Because the
.PN 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
.PN rwhod
daemon is disabled by default.  To make use of the
.PN rwhod
daemon for both the local and remote hosts,
remove the comment symbols (#) from in front of the lines specifying
.PN rwhod
in the
.PN /etc/rc
file.
.PP
If the
.PN rwhod
daemon is not running on a remote machine, the machine
may incorrectly appear to be down when you use the
.PN ruptime
command to determine its status.  See the
.MS ruptime 1c
reference page for more information.
.PP
If a system has more than 40 users logged in at once, the number
of users displayed by the
.MS ruptime 1c 
and 
.MS rwho 1c 
commands is incorrect.
Users who login after the fortieth user, will fail to appear 
in the output of the 
.MS ruptime 1c 
and 
.MS rwho 1c 
commands. This is because the maximum size limit of an Ethernet packet
is 1500 bytes, and the 
.PN rwhod 
daemon must
broadcast its information in a single packet.
.SH See Also
ruptime(1c), rwho(1c)