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RE: Thanks and Suggestions
 

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novashadow at msn

Mar 1, 2009, 7:09 PM


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RE: Thanks and Suggestions [In reply to]

Thank you Mr. Lanning,

I tried your suggestion, see below, and it does work like I want, but I have 2 questions.

> ssh joe [at] example "sleep 1000 < /dev/null> /dev/null 2>&1 &"

1) I see a lot of scripts use the form /dev/null> /dev/null 2>&1 rather than < /dev/null> /dev/null 2>&1. Why don't you want/need the latter in scripts?

2) If I enable logging for my remote ssh command, which is an ssh command, will < /dev/null> /dev/null 2>&1 change logging in any way?

> Date: Sat, 28 Feb 2009 03:28:18 -0800
> Subject: Re: Thanks and Suggestions
> From: robert.lanning [at] gmail
> To: secureshell [at] securityfocus
>
> I am not an OpenSSH developer...
>
> On Fri, Feb 27, 2009 at 8:03 PM, Chris Mirchandani wrote:
>> 3) Maybe this already exits, so maybe this is not a request. Would like an easy to use
>> command that lets us see all the forwards and tunnels on a computer. I should be
>> able to limit to one or multiple types, local, remote, dynamic, remote dynamic (if
>> my request is added), tunnels initiated locally and tunnels initiated remotely. Should
>> be options for all forwards only, all tunnels only everything and if you could use the
>> inclusive options and exclude ones you do not want in the list. It would be great if
>> I could set a specific log just for this and so that ever time thius changes it updates
>> that log with the change or all the connections with the changes highlighted. e.g.
>> added in front of each that was added and removed for those that were closed. No,
>> gSTM (http://sourceforge.net/projects/gstm/) is not an alternative for what I am suggesting.
>
> I believe this would be a huge security information leak. And would
> advise against
> implementation.
>
>> 4) Command that can show all ssh connections, remote and local.
>
> If you need more than what "ps" or "netstat -anp", then I will refer
> you to my answer to
> suggestion 3.
>
>>
>> Question
>>
>> Is there a way to send a command via ssh that stays open even if the the ssh session
>> that created it closes? I have this figured out already, I think, but my problem is that my
>> ssh session does not close like it normally does after a command is run and completed.
>> So maybe my real question is, how do I do this and have the ssh session close after the
>> command is run? e.g. If I run the following command, I get output and the ssh command
>> closes. Of course the command I am running in this example, has an end, but the one I
>> want to use does not.
>>
>> ssh -p 4731 root [at] localhos netstat -an | egrep "tcp.*:3731.*LISTEN"
>>
>> However, if run one of the following commands, the remote command works, but am
>> not returned to the command prompt. I have to kill the ssh connection to be returned to
>> a prompt and the remote command stays running after I kill the initial connection, but
>> this does not help me in a script.
>>
>> $ ssh -p 4731 root [at] localhos 'ssh -q -N -D 1873 -p 3731 sshd [at] localhos &'
>> $ ssh -p 4731 root [at] localhos ssh -q -N -f -D 1873 -p 3731 sshd [at] localhos
>>
>> Btw, the fact that I am using localhost does not mean that all connections are to the
>> same computer. The ports are forwards. I know I can send the local command to the
>> background, but there is no need to keep it open, i want to to close like it does with
>> ssh -p 4731 root [at] localhos netstat -an | egrep "tcp.*:3731.*LISTEN".
>
> OpenSSH will close its connection, when no-one else has the terminal/pipe open.
> This means more than just backgrounding the job. ("&")
>
> You must redirect STDIN, STDOUT and STDERR to somewhere else and background
> the job.
>
> $ date
> Sat Feb 28 03:18:38 PST 2009
> $ ssh joe [at] example "sleep 1000 < /dev/null> /dev/null 2>&1 &"
> $ date
> Sat Feb 28 03:18:41 PST 2009
>
> So, with that, I redirected STDIN ("< /dev/null") and STDOUT (">
> /dev/null") then
> made STDERR (2) go to the same place as STDOUT (1) ("2>&1"). Then the whole
> command gets backgrounded ("&").
>
> --
> And, did Galoka think the Ulus were too ugly to save?
> -Centauri

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Subject User Time
Thanks and Suggestions novashadow at msn Feb 27, 2009, 8:03 PM
    Re: Thanks and Suggestions robert.lanning at gmail Feb 28, 2009, 3:28 AM
    RE: Thanks and Suggestions novashadow at msn Feb 28, 2009, 8:44 PM
        Re: Thanks and Suggestions robert.lanning at gmail Mar 1, 2009, 3:51 PM
    Re: Thanks and Suggestions bala.linux at gmail Mar 1, 2009, 6:44 AM
    RE: Thanks and Suggestions novashadow at msn Mar 1, 2009, 7:09 PM
        Re: Thanks and Suggestions robert.lanning at gmail Mar 2, 2009, 12:44 AM
        Re: Thanks and Suggestions wooledg at eeg Mar 2, 2009, 1:34 PM

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