Hi,
Can you do a ‘zypper dup’ from Tumbleweed to Leap 15? Or is that not advisable?
AFAIK LEAP 15 has been tested for upgrade only from a fully updated LEAP 42.3 (see also https://en.opensuse.org/SDB:System_upgrade for more details).
That said, since LEAP 15 was based on a TW version of a few months ago, upgrading from current TW might work too, but nobody is going to guarantee that.
If you are willing to experiment and prepared to do a “fresh install” if something goes wrong, you might try that.
Be sure to backup ALL your data beforehand.
And… sorry but I accept no liability for the above 
If you’re on btrfs, you should be able to boot in a previous snapshot if things don’t work out well. But I think it should work. With the additions @OrsoBruno already mentioned.
It wouldn’t be a problem to do a fresh install, and there is no data to backup. I just want to do the ‘zypper dup’ because it’s faster and easier, so I’ll probably try it…
But the machine will be a production server in the future, so I don’t want to get problems later on because it was an “upgrade” from tumbleweed and not a fresh install.
On 2018-06-07, wvv <wvv@no-mx.forums.microfocus.com> wrote:
> But the machine will be a production server in the future, so I don’t
> want to get problems later on because it was an “upgrade” from
> tumbleweed and not a fresh install.
If the machine will be a production server, I would strongly advised against TW and start with a fresh Leap install.
I installed TW as a test, and I came to the same conclusion, it’s not suitable for production…
and start with a fresh Leap install.
That’s what I’m contemplating. 
Well, in many cases – though not most, I would guess – it is suitable for production.
But, almost certainly not suitable for a production server.