Re: TRAMP password caching

[Michael Albinus]

Eli Zaretskii <address@hidden> writes:

Hi Eli,

>> For openssh like implementations, I've (tried to) fix(ed) it by adding
>> ControlMaster/ControlPath arguments to the "scp" commands. AFAIK,
>> these arguments are not available under w32, so it shall be checked
>> whether "pscp" is still the preferrable default method.
>
> I checked this now: on Windows, pscp behaves like scp and plink
> behaves like ssh on Posix platforms.  In other words, we should indeed
> change the default method on w32 to plink, because that is faster and
> asks for the passphrase fewer times.

That was the default until recently. It was changed because people
regard ssh (aka plink) methods too slow for copying large files.

>> Of course, one would be on the safe side when PuTTY's pageant is
>> running (the ssh-agent pendant). Maybe one could check this during
>> initialization, and set tramp-default-method to either "plink" or
>> "pscp", depending on the result.
>
> I will try to see if this can be done easily from within a running
> Emacs.

Please do. I hoped it could be determined simply via the existence of
environment variables (as it is possible with ssh-agent, environment
variables $SSH_AUTHENTICATION_*), but it doesn't seem so easy. And I
also don't know a command like 'ps' which returns running processes,
in order to check whether pageant is active.

> Btw, why does pscp method work so hard when pageant is not running?  I
> see a lot of activity, including remote shell setup, remote `ls'
> command to get a directory, sending Perl scripts to the remote
> machine, etc.  Why doesn't it simply invoke pscp to copy the darn
> file?  Is it for file-name completion, perhaps? if so, maybe we should
> give users a way of disabling completion?

All Tramp methods provide a whole implementation of primitive file
operations. Not only for `copy-file' or `rename-file', but also
`file-attributes' or `directory-files' etc. Those functions cannot be
implemented by (p)scp, I fear. Because of this, Tramp opens
additionally an ssh resp. plink connection.

Best regards, Michael.