From: Alan Claughan <alan@...>
Date: 2009-05-19T02:23:22+09:00
Subject: Re: Desperate help needed with SSH

Hi Sandor

Thanks for the reply.

The host I am connecting to is a Cisco Router. The commands definitely  
work on a manual SSH session from my terminal

The first command always works.
I get the channel failure when trying to run the second command.
I tried swapping the two commands around, but I get the same failure.

I used the following code to talk to my mac:

require 'rubygems'
require 'net/ssh'

  Net::SSH.start('127.0.0.1', 'user', :password => 'password') do |ssh|
    ssh.exec "ls -al"
    ssh.exec "pwd"
    ssh.exec "ps -axe"
    ssh.loop
  end

Which worked great. I then changed the IP address and replaced the  
commands with router commands:

require 'rubygems'
require 'net/ssh'

  Net::SSH.start('10.0.255.1', 'name', :password => 'password') do |ssh|
    ssh.exec "sh ver"
    ssh.exec "cdp ne"
    ssh.loop
  end

And it fails at the second ssh.exec, so I'm guessing this is related  
to the Cisco SSH Server.

Alan.

On 17 May 2009, at 12:26 AM, Sandor Szücs wrote:

>
> On 13.05.2009, at 11:05, alan@isdial.net wrote:
>> -- snip --
>>
>> require 'rubygems'
>> require 'net/ssh'
>>
>> hosts = ['10.0.255.1' , '10.0.255.2' , '10.0.255.3']
>>
>> instructions = [
>> 'sh version',
>> 'sh cdp ne'
>> ]
>
> These instructions looks strange for me. Are you sure that these run
> on all hosts?
>
> Try to use other instructions that should work like
> ["echo foo", "sh -c 'echo bar'"]
>
> Maybe your instructions kill the shell environment by calling exec
> or something similar.
>
>> hosts.each do |host|
>> Net::SSH.start(host, 'user', :password => 'password') do |ssh|
>    File.open("output/#{host}.txt", 'w') do |fn|
>>
>>   instructions.each do |command|
>>     fn.puts "|--------\[#{command}\]--------------------------"
>>     fn.puts ssh.exec!(command)
>>   end
>   end
>>
>> end
>> end
>>
>> -- snip --
>
> This part should be ok, but you can improve your code and use a block
> for File.open().
>
> File.open("output/#{host}.txt", 'w') do |fn|
>  ..
> end # fn.close not needed, because the block end close the file  
> already.
>
>> When I run this I get the following error :
>>
>> Net::SSH::ChannelOpenFailed: (4)
>>
>> If I remove the instructions.each loop and run only a single  
>> command. Life
>> is good and it all works. If I add a second ssh.exec! or the loop,  
>> the
>> error returns.
>
> Calling ssh.exec!() twice in a session is not a problem.
>
> irb> Net::SSH.start(host, user, :password => passwd) do |ssh|
> irb>   ['sh -c "echo foo"', 'echo bar'].each do |command|
> irb>    puts ssh.exec!(command)
> irb>   end
> irb> end
> foo
> bar
>
>
> hth. regards, Sandor Szücs
> --
>
>
>
>