Re: TRAMP and scp

[Kai Grossjohann <kai.grossjohann@gmx.net>]

Michael Powe <michael+gnus@trollope.org> writes:

> Out of band method `scp' not applicable for remote shell asking for
> a password

It seems I failed to describe this correctly.  Here is how Tramp
works:

When you invoke something that invokes Tramp, Tramp first opens a
shell connection to the remote host.  This shell is used for filename
completion and suchlike.  For this shell connection, Tramp knows how
to deal with password prompts.

If you are using an out-of-band method, then on actually transferring
a file, Tramp will open another connection to the remote host, using
scp in your example.  For this connection, Tramp does NOT support
password prompts.

So an easy workaround is to choose an inline method, such as ssh.  (It
will use uuencode or mimencode to transfer the file contents through
the shell connection.)

It would not be too difficult to support password prompts for scp
invocations.  But then Tramp would ask you on every I/O operation,
such as C-x C-f or C-x C-s.  Or autosave, for that matter!

So to make Tramp support scp password prompts in a meaningful manner,
it would have to cache the password.  I was afraid of the security
issues involved, and so I wasn't so motivated to doing this.  However,
if somebody else does it then I'll be happy to include that work.
(Modulo paperwork issues.)

Oh, one thought just pops into my mind: would it have helped if the
message had mentioned that you can use inline methods instead?  I
could say `Use an inline method instead of the out-of-band method
`scp' because your remote shell asks for a password.'  Would that have
helped?

-- 
Two cafe au lait please, but without milk.