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Re: ftp & multi-hop?

From: sp1ff
Subject: Re: ftp & multi-hop?
Date: Mon, 27 Oct 2003 21:22:04 +0000

Michael Albinus <address@hidden> writes:

> "Kai Gro├čjohann" <address@hidden> writes:
>>> I would like to connect to an ftp server in two hops.  One over `sshx'
>>> to a server behind a firewall, and thence via ftp to a second server
>>> inside that firewall.  Now I understand that 'ftp isn't a member of
>>> `tramp-multi-connection-function-alist', so this isn't supported
>>> out-of-the-box.
> [...]
>> So whereas multi-hop-with-inline just needs a single shell, doing multi-hop
>> with out-of-band methods requires O(n) shells where n is the number of hops.
>> FTP is similar to an out-of-band method because the protocol has a control
>> connection (for sending commands like cd and dir) and then establishes
>> additional data connections for actual file transfer.
> One could allow out-of-band methods as _last_ hop only. This would
> reduce the logic to 2 connections. And for methods like ftp and smb it
> wouldn't make sense otherwise.

I'm looking at `tramp.el', and I'm wondering if we could define a
method that would do just this.  I.e. only be permitted as the last
hop, and use ftp (or any out-of-band mechanism, I suppose).  I suppose
we'd need to define an action that could be handled by
`tramp-process-multi-actions', yes?  Or would this be a real kludge?
I'm new to `tramp' ...  BTW - what's 'smb'?

>> But maybe the good news is that Ange-FTP itself supports a so-called
>> "gateway" feature.  I never really grokked what that does, but it seems you 
>> can tell
>> it to rsh to another host to invoke ftp from there.  I think Ange-FTP can
>> then use rcp to transfer the files between the local system and the gateway
>> host.  Ange-FTP stems from the before-SSH times, but I guess that whatever 
>> its
>> methods are for rsh/rcp, they can be adapted to use ssh/scp instead.
> It's a nice idea to map 
> /multi:ssh:address@hidden:ftp:address@hidden:/path/to.file
> on Ange-FTP gateways. Worth a try.

Well, according to the docs, in order to get the gateway option to
work with `ange-ftp', one has to:

   Using NFS and symlinks, make sure that there is a shared directory with
   the *same* name between the local machine and the gateway machine.
   This directory is necessary for temporary files created by ange-ftp.

That's not going to happen in my case.

  Michael Herstine

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