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

[Jamie C. <jca...@we...>]

On 16/Oct/2022 03:59 Christopher Pinon <cj...@ex...> wrote ..
> 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.

Does the "rmt" command exist on your NetBSD system, and if so in what
location? I seem to recall that it's different from on Linux, and this can
cause remote tar backups to fail because the tar command expects to be
able to run it.

> 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). :-(

Sure, that would be useful! You can contact me off-list with the details ..