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 19:24, Jamie Cameron a écrit :
> 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.

Yes, in fact, I had already looked into this. rmt is indeed present (by 
default) on NetBSD, and its path is the same as on my Linux systems: 
/usr/sbin/rmt . So my conclusion was that this wasn't an obstacle.

>> 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 ..

I'll send you the details to your webmin address within 15 minutes. 
Thanks for being willing to look into this. If it works for you right 
away, I may need to seriously question my sanity! :-D

C.