cwall(1M)cwall(1M)NAMEcwall - Displays a wall(1M) broadcast message on multiple hosts. cwall
is part of the Distributed Systems Administration Utilities (DSAU).
SYNOPSIS
Path: /opt/dsau/bin/cwall
[-g | --groupname groupname] [filename]
{-h | --help | ? }
{-V | --version}
DESCRIPTION
distributes broadcast messages to multiple hosts. In a Serviceguard
cluster, the messages are displayed on all cluster members by default.
When not in a cluster, host options must be specified or else defaults
to displaying the message for only the local host.
messages are broadcast messages displayed on the terminals of all
logged-in users. Users can block the receipt of broadcast messages
using . The -g or --groupname options send the message only to members
of the specified group in /etc/groups.
REMOTE COMMAND TRANSPORT OPTIONS
You can select how connects to target systems at runtime using the -R
option. ssh is the default transport. The following protocols are
supported:
· rsh : Uses an internal, thread-safe implementation of BSD to
run commands using the standard protocol.
· (default): Uses a variant of to run multiple copies of the
command.
Options
-a reads the /etc/machines file to obtain the list of nodes.
This option has no arguments. Note that /etc/machines is not
shipped by default and can be created on a per-host basis.
The format for the /etc/machines file is the same as that for
the --hostsfile described below.
-f | --hostsfile filename
Runs the commands listed in filename on all nodes listed in
hostsfile. The specified files should contain a list of tar‐
get hosts, one per line. Hostlist specifications are valid.
See HOSTLIST EXPRESSIONS below.
--fanout number
Set the fanout width, the maximum number of simultaneous
remote commands, to number. For example, with 100 hosts and
of 10, DSAU contacts 10 hosts at a time.
- g | --groupname groupname
Display the message only to members of the specified group in
/etc/groups.
-h | --help
Display command help and quit.
-l | --list
List valid signal names.
-n | -w | --nodes host1,host2,...
Target the specified list of hosts. No spaces are allowed in
the comma-separated list. The host list may contain hostlist
expressions such as ``host[1-5,7]''. For more information
about the hostlist format, see the HOSTLIST EXPRESSIONS sec‐
tion below. This option overrides all other host specifica‐
tion options.
-R | --rcmd {rsh | ssh}
Set remote command transport to rsh or ssh.
-t | --timeout seconds
Set the connect timeout in seconds.
-u | --ctime seconds
Set a limit on the amount of time a remote command is allowed
to execute. Default is no limit.
--user username
Execute remote commands as username.
-V | --version
Shows the version of .
-x | --exclude host1,host2,...
Exclude the specified hosts. Host lists may also be speci‐
fied with the option (see the HOSTLIST EXPRESSIONS section
below).
ENVIRONMENT VARIABLES
On non-Serviceguard clusters, if no other node selection option is
used, the CFANOUT_HOSTS environment variable may be set to a filename
from which a list of target hosts is read. The file must contain a
list of hosts, one per line. Hostlist expressions are allowed.
LIMITATIONS
When using the transport, non-interactive must have already been con‐
figured between the source and destination hosts. does not interac‐
tively prompt for passwords. Use the tool to help you configure non-
interactive ssh. Similarly, when using rsh, the .rhosts files on the
nodes must be properly configured. The connect timeout (-t or --time‐
out) is not adjustable when using ssh.
The number of nodes on which can simultaneously execute remote jobs is
limited by the maximum number of threads that can be created concur‐
rently, as well as the availability of reserved ports in the rsh mod‐
ules. For additional limitations, see the manpage.
HOSTLIST EXPRESSIONS
accepts lists of hosts in the general form: prefix[m-n,k-l,...], where
m < n and k < l. These expressions are alternatives to explicit lists
of hosts. Do not confuse this form with regular expression character
classes that are also denoted with []. For example, node[19] does not
represent an expression matching node1 or node9, but represents the
expression node19.
Using hostlist expressions is optional. They are particularly useful
when a group of systems uses a prefixNNN naming convention. With this
capability, you could either specify node1,node9 or use the hostlist
expression node[1,9].
EXAMPLES
In a Serviceguard cluster, display a message cluster-wide:
# cwall
Package X is being stopped temporarily for maintenance
^D
where ^D is Control-D or end-of-file.
To display a message on terminals of specified hosts:
# cwall-w host1,host2,host[3,5,7-11] filename
where filename contains the message to display.
SEE ALSO
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cwall(1M)
