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Re: [ptp-user] SFTP & login shell access different for same connection
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Hi Greg,
Thanks for the detailed explanation. Unfortunately I don't have any
influence over the cluster SSH access policy, but your alternative does
sound interesting. I'm usually a poor beta tester because the spare
cycles I have to devote to things like this usually come in
widely-separated bunches, but I'd be happy to try it out so long as
you're not counting on me to give you feedback quickly. :) I have no
problem waiting until next week -- I can certainly grind along with my
current non-Eclipse workflow until there's something to use.
-Jeremy
On 05/12/2016 11:28 AM, Greg Watson wrote:
PTP uses the ssh connection for two things: to launch remote
processes; and to access files on the remote system. It does this
using ssh “channels”, which are part of the ssh specification. It
uses an “exec" channel for processes, and an “sftp" channel for
files. Unfortunately, some systems either limit the number of
channels to one, or as it appears in your case, don’t provided an
sftp service at all. Incidentally, yours is the first case I’ve come
across where this is the case.
While it would theoretically be possible to get around this problem
by allowing the exec and sftp channels to be handled by separate ssh
connections, this would be a bit of a pain for the user, since they
would have to log on twice each time a connection was opened (or in
your case, log on to two different machines). Also, the architecture
is currently that a new exec channel is opened for every remote
process, so this would necessitate a user constantly logging in (at
least for the case where channels are limited to one.)
I’m currently working on another approach, which is to use a single
ssh connection, but run a small agent at the remote end (that gets
automatically uploaded the first time you use PTP). The agent would
handle process creation and filesystem access, and multiplex this
over the single connection. The agent uses the TCF protocol, and is
written in python, so will require python to be installed on the
remote machine (I don’t know of any Linux systems where this is not
the case.) Another possibility would be to use the C based agent that
comes with TCF, but that is about 1MB, so would probably need to be
installed manually.
So, if you’re happy to wait (and are interested in being a guinea
pig) then I should have something you can try by next week. Otherwise
the only option is to enable sftp on the remote machine.
Greg
On May 12, 2016, at 9:56 AM, Jeremy Wolcott
<jeremy.wolcott@xxxxxxxxx> wrote:
Hi,
I'd like to create a synchronized project which synchronizes from
my laptop to a HPC cluster system that I use. I'm being flummoxed
by one aspect of the cluster: login shell access and SFTP access
are provided via different machines, e.g. login.example.com and
sftp.example.com. It appears that PTP needs both: login for the
git part, and SFTP for something I don't quite understand. (If I
try to use the login server in the 'connection' I create with
Eclipse, I get this error: "Remote host does not support sftp.
Remote functionality requires sftp to be enabled").
Is there some way of specifying different hosts for shell and SFTP
access? I can't find one in the connection configuration.
Thanks!
-Jeremy Wolcott _______________________________________________
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