Re: [webmin-l] Issue with backing up *via ssh* from a Linux system to a NetBSD system using the "Filesystem Backup" module

[Christopher P. <cj...@ex...>]

Le 2022-10-16 07:53, Jamie Cameron a écrit :
> On 15/Oct/2022 11:58 Christopher Pinon <cj...@ex...> wrote ..
>> Le 2022-10-15 18:49, Jamie Cameron a écrit :
>> > On 15/Oct/2022 06:30 Christopher Pinon <cj...@ex...> wrote ..
>> >> Hi,
>> >>
>> >> I've been using Webmin for a few years and am currently using v. 2.000
>> >> .
>> >>
>> >> I've noticed a significant issue with backing up *via ssh* from a
>> >> Linux
>> >> system to a NetBSD system using the "Filesystem Backup" module. In
>> >> fact,
>> >> this is an issue that I've always experienced with Webmin, but I
>> >> thought
>> >> that I would finally ask about it. :-)
>> >>
>> >> First of all, backing up *via ftp* from Linux to NetBSD works fine
>> >> (whether by dump or by tar), and this is what I've been doing.
>> >>
>> >> However, backing up *via ssh* from Linux to NetBSD doesn't work for
>> >> some
>> >> reason. If I start a backup from Linux to NetBSD, the process begins
>> >> and
>> >> takes a long time and finally gives up (or after a long time, I give
>> >> up
>> >> and terminate the process). There's never ever any trace of the dump
>> >> or
>> >> tar file on the NetBSD system.
>> >>
>> >> (As a sanity check, backing up via ssh from Linux to Linux *does* work
>> >> for me.)
>> >>
>> >> Naturally, ssh/sftp work fine on the NetBSD system -- after all, it's
>> >> (standard) OpenSSH.
>> >>
>> >> Webmin doesn't display any error message, as far as I can tell: the
>> >> backup process simply doesn't succeed after a long while. None of the
>> >> files miniserv.error , miniserv.log , or webmin.log seems to indicate
>> >> that anything went wrong, as far as I can tell.
>> >>
>> >> I wanted to ask: is this a known issue? Where could I look for the
>> >> source of the error?
>> >>
>> >> I'd be grateful for any advice.
>> >
>> > Hi Christopher,
>> >
>> > Are you using a password to authentication via SSH to the remote
>> > system,
>> > or a private key? Also, can you SSH with the same credentials from the
>> > command line on your Webmin system?
>> >
>> >  - Jamie
>> 
>> Hi Jamie,
>> 
>> I'm using a password to authenticate via ssh on the remote (NetBSD)
>> system. (All of my backup tests via ssh with Webmin from Linux to 
>> NetBSD
>> and from Linux to Linux have used a password to authenticate.)
>> 
>> On the command line of the Linux system (where Webmin is installed), I
>> can use ssh/sftp/scp to reach my account on the remote NetBSD system. 
>> In
>> fact, I've just tried all three of these commands and they work!
>> 
>> Even so, any attempt to use the "Filesystem Backup" module of Webmin 
>> on
>> the Linux system to back up via ssh a (small) directory to the NetBSD
>> system fails. Basically, the process takes many-many minutes -- it 
>> seems
>> to hang -- before it finally gives up (or I kill it), with absolutely 
>> no
>> result.
>> 
>> In contrast, choosing to use ftp in the module works fine.
>> 
>> I've experienced this issue since I began to use Webmin, which was
>> around four years ago.
> 
> Hi Christopher,
> 
> What if you backup from your Linux system to a different Linux system,
> rather than NetBSD? That would be a useful test to figure out if the
> issue is coming from the client or server side..
> 
>  - Jamie

Hi Jamie,

Yes, backing up (via ssh in the Webmin module) from the Linux system to 
a different Linux system works fine. I've just tested this again.

But again, backing up (via ssh in the Webmin module) from the same Linux 
system to the NetBSD system doesn't work. In fact, I've just tried to 
back up to two different NetBSD systems, and neither works. In contrast, 
backing up via ftp works.

I'd agree that it looks like NetBSD is the problem here, but at the same 
time, on both (up-to-date) NetBSD systems, we're talking about 
garden-variety sshd (from OpenSSH) with barely any custom configuration 
(the only customized change is that X Forwarding has been turned on). 
Add to this that I can ssh/sftp/scp on the command line from the Linux 
system to either NetBSD system without difficulty.

So it's a puzzle to me. In addition, as I said in my initial message 
(above), Webmin doesn't provide any error message in this case: the 
process just seems to fall into a loop and to take a very long time. On 
my most recent attempt, the circle for "Save and Backup Now" is still 
spinning without any error message after more than an hour, whereas a 
backup via ftp of the same small directory takes less than 10 seconds.

C.

P.S.: If you would like to try to replicate this issue, I'd be happy to 
give you a temporary shell account on one of the NetBSD systems. I often 
wonder whether I'm missing something obvious, which is possible, despite 
my numerous tests/attempts (which is also why I hesitated to write to 
the mailing list). :-(