ssh and netcatOct 03 2009 12:00AM Josef Wolf (jw raven inka de) (2 replies)
Re: ssh and netcatOct 05 2009 10:53PM Darren Tucker (dtucker zip com au) (1 replies)
Josef Wolf wrote:
> I can get rid of this error message by deleting the "exec" keywords from
> the above script. But this effectively ignores the error.
>
> So the question is: what causes this "Killed by signal X"? Is it some sort
> of incompatibility between ssh and netcat?
The "outer" ssh command sends a SIGHUP to the proxycommand when it shuts
down (some versions of netcat don't check for the closure of their
stdin/stdout and would hang around forever).
By default, if ssh is killed by a signal it reports which one, which is
what you're seeing (on Linux, 1=SIGHUP, 2=SIGINT).
> Or am I using ssh and/or netcat
> in a way it was not designed for? Any ideas how to properly get rid of this
> error?
You can either keep doing what you're doing (without the "exec", the ssh
command has a parent shell, and the shell catches the SIGHUP but it does
keep the shell process around for the duration of the connection) or
tell ssh to be quiet and not report the signal (change "exec ssh foo" to
"exec ssh -q foo").
--
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4 37C9 C982 80C7 8FF4 FA69
Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.
> I can get rid of this error message by deleting the "exec" keywords from
> the above script. But this effectively ignores the error.
>
> So the question is: what causes this "Killed by signal X"? Is it some sort
> of incompatibility between ssh and netcat?
The "outer" ssh command sends a SIGHUP to the proxycommand when it shuts
down (some versions of netcat don't check for the closure of their
stdin/stdout and would hang around forever).
By default, if ssh is killed by a signal it reports which one, which is
what you're seeing (on Linux, 1=SIGHUP, 2=SIGINT).
> Or am I using ssh and/or netcat
> in a way it was not designed for? Any ideas how to properly get rid of this
> error?
You can either keep doing what you're doing (without the "exec", the ssh
command has a parent shell, and the shell catches the SIGHUP but it does
keep the shell process around for the duration of the connection) or
tell ssh to be quiet and not report the signal (change "exec ssh foo" to
"exec ssh -q foo").
--
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4 37C9 C982 80C7 8FF4 FA69
Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.
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