Re: SSH

[Cameron Simpson <cs zip com au>]

On Thu, May 31, 2001 at 03:51:55PM -0400, Krister Bruhwel <bruhwel jlab org> wrote:
| Does anyone know how to scp thru a machine.  I can use "ssh -t mach1 ssh
| mach2"  to ssh thru a machine.  I would like to do something like that
| with scp.  
| If another newsgroup would be better, please tell of it.

Short answer: to can't do it like the ssh line you describe.
Middle anser: you can half do it.
Cunning answer: you can do it in full with a port forward (I do this at home).
	        details after the "Middle Answer".

Middle Answer
=============

This will do it:

	ssh mach1 ssh mach2 cat file >local-file

You could write a script you do it, too, but it will be a real pain to
support all the frills of a proper scp (-r -p etc etc).

If you have to copy more than a single file you're best using an archive
program like tar or a tool like rsync. You can then:

	ssh mach1 ssh mach2 tar cf - lots-of-stuff | tar xvf -

or
	tar cf - local-stuff | ssh mach1 ssh mach2 tar xvf -

Cunning Answer
==============

Arrange a stable ssh connection to mach1 with a port forward to mach2:

	ssh -f -L 2022:mach2:22 mach1 'while sleep 60; do :; done'

Make a Host record in your ~/.ssh/config:

	Host mach2viaMach1
		Hostname	mach1
		Port		2022

Then you can go

	ssh mach2viaMach1

or

	scp mach2viaMach1:file blah

Effectively you're letting mach2's sshd listen for connections on port 2022
on your local machine.

This works really well.
-- 
Cameron Simpson, DoD#743        cs zip com au    http://www.zip.com.au/~cs/

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