That is basicaly the prodedure as described since a rather long time as “change the repos to point to the new ones and do zypper dup”. Of course amended by some extra precautions, etc.
This thread is about an improvement made. Instead of changing the string 15.1 to 15.2 in the repo definitions, one could (should?) change 15.1 to $releasever. And then do the zypper dup as
zypper --releasver 15.2 dup
This has the advantage that it will also work in the future on 15.3, etc. without doing all the edits.
We also found out that from a fresh installation of 15.1 onwards, this $releasever string is already put into the repo list, and this will work as now is advertised in the documentation.
However, when the fresh install was done with 15.0 or earlier and upgraded with the “edit the repos” way, the $releasever will not be in your 15.1 repo list and the advertised way of using --releasever will thus not work. Changes to the documentation were made a few days ago, but I have no idea if that was done in all places were the upgrade description is documented.
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I will repeat (from this and another thread), that you can not find if $releasever is used in your rep list by doing e.g.
zyper lr -d
because zypper will replace all $releasever with the current version. Thus on a 15.1 system the URIs will show 15.1 regardless if there is 15.1 or $releasever in the list.
One way to see what is in the repo lists is
grep baseurl /etc/zypp/repos.d/*.repo
Another, more funny, way of looking at it is
zypper --releasever FOO lr -d
It will show 15.1 when there is no $releasever and FOO if there is. So if at least all standard repos URIs are shown with FOO, you are ready for the future.