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Expect Issue Serial Forground Execution vs Concurrent Background Execution

 
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Old 09-14-2009
Expect Issue Serial Forground Execution vs Concurrent Background Execution
I have an expect script that interrogates several hundred unix servers for both access and directories therein using "ssh user@host ls -l /path". The combination of host/path are unique but the host may be interrogated multiple times if there are multiple paths to test.

The expect script is run from a wrapper script that reads thru a file containing the host/path pairs. When I spawn off the expect script in the background without waiting for completion the result are, in some cases, quite different from when the expect script is run one at a time.

The error encountered when spawning off many expect scripts is "ssh_exchange_identification: Connection closed by remote host" which never happens when the expect script is run sequentially with implied wait.

Is the problem that a given server is being hit too fast with multiple ssh connection attempts or something else?

Any and all thoughts appreciated.

twk
 
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LEARN ABOUT ULTRIX

ssh-keysign

ssh-keysign(1M) 														   ssh-keysign(1M)

NAME

       ssh-keysign - ssh helper program for host-based authentication

SYNOPSIS

       ssh-keysign

       ssh-keysign  is	used  by ssh(1) to access the local host keys and generate the digital signature required during host-based authentication
       with SSH protocol version 2. This signature is of data that includes, among other items, the name of the client host and the  name  of  the
       client user.

       ssh-keysign  is	disabled  by  default and can be enabled only in the global client configuration file /etc/ssh/ssh_config by setting Host-
       basedAuthentication to yes.

       ssh-keysign is not intended to be invoked by the user, but from ssh. See ssh(1) and sshd(1M) for more information about host-based  authen-
       tication.

       /etc/ssh/ssh_config

	   Controls whether ssh-keysign is enabled.

       /etc/ssh/ssh_host_dsa_key
       /etc/ssh/ssh_host_rsa_key

	   These  files  contain the private parts of the host keys used to generate the digital signature. They should be owned by root, readable
	   only by root, and not accessible to others. Because they are readable only by root, ssh-keysign must  be  set-uid  root  if	host-based
	   authentication is used.

       ssh-keysign will not sign host-based authentication data under the following conditions:

	 o  If the HostbasedAuthentication client configuration parameter is not set to yes in /etc/ssh/ssh_config. This setting cannot be overri-
	    den in users' ~/.ssh/ssh_config files.

	 o  If the client hostname and username in /etc/ssh/ssh_config do not match the canonical hostname of  the  client  where  ssh-keysign	is
	    invoked and the name of the user invoking ssh-keysign.

       In  spite of ssh-keysign's restrictions on the contents of the host-based authentication data, there remains the ability of users to use it
       as an avenue for obtaining the client's private host keys. For this reason host-based authentication is turned off by default.

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWsshu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

       ssh(1), sshd(1M), ssh_config(4), attributes(5)

AUTHORS

       Markus Friedl, markus@openbsd.org

HISTORY

       ssh-keysign first appeared in Ox 3.2.

								    9 Jun 2004							   ssh-keysign(1M)