RWHOD(8) | System Manager's Manual | RWHOD(8) |
NAME¶
rwhod
— system
status server
SYNOPSIS¶
rwhod |
[-bpa ] [-u
user] |
DESCRIPTION¶
Rwhod
is the server which maintains the
database used by the rwho(1) and
ruptime(1) programs. Its operation is predicated on the
ability to
broadcast
messages on a network.
Rwhod
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
/var/spool/rwho.
The server transmits and receives messages at the port indicated in the ``rwho'' service specification; see services(5).
If the -b
flag is supplied, only broadcast
interfaces, such as ethernets, will be used. If the
-p
flag is supplied, only point-to-point interfaces
will be used. If the -a
flag is supplied, or no
flags are supplied, all interfaces will be used.
If the -u
flag is supplied, rwhod will run
as the specified user instead of as root.
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(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 in an integer. The host name included is that returned by the 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 utmp(5) entry for each non-idle terminal line and a value indicating the time in seconds since a character was last received on the terminal line.
Messages received by the rwho server are
discarded unless they originated at an 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
/var/spool/rwho. These files contain only the most
recent message, in the format described above.
Status messages are generated approximately once every 3 minutes.
Rwhod
recomputes the system boot time every 30
minutes because on some (non-Linux) systems it is not a totally reliable
process.
SEE ALSO¶
BUGS¶
There should be a way to relay status information between networks. People often interpret the server dying or network communtication failures as a machine going down.
HISTORY¶
The rwhod
command appeared in
4.2BSD.
May 13, 1997 | Linux NetKit (0.17) |