Re: TRAMP and scp

[Michael Powe]

hello,

thanks for the extended reply.

>>>>> "Kai" == Kai Grossjohann <kai.grossjohann@gmx.net> writes:

    Kai> Michael Powe <michael+gnus@trollope.org> writes:
    >> Out of band method `scp' not applicable for remote shell asking
    >> for a password

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

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

okay, so under what circumstances does this occur with scp, which i
believe is the default method if i don't use tramp-default-method? 

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

the message cited is the first message i get from attempting to open a
file remotely, so i don't actually get a prompt even for the opening
connection. that confuses me.  from your description, it sounds like i
should get an initial password prompt and then the secondary attempt
to connect to the file (after opening the shell) should fail.

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

so, if i (setq default-tramp-method "ssh"), that performs the same
function? i shall try it forthwith.

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

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

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

i'm afraid i don't actually know the difference between "inline" and
"out-of-band" in this context, although your description here of what
is happening is clear.

thank you.

mp

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