4.0.2RC was a development version and migrating to Stable is not supported in
any way (that's why devel has a warning about that, at the website, maybe we
should add other at the YaST2 installer).
Your case is even more tricker than usual as you are on openSUSE 15.0 and not
openSUSE 15.1, so I am not 100% sure that the migration script that we
prepared will work.
But that said, I can give you the same advice I gave to David Mace at the
thread "repo issue?"
First of all: take a full backup of the server with whatever method you have
available, so you can restore if there are problems.
- Take note of your current susemanager-schema version (4.0.X, let's call it
current_version) (rpm -qa|grep susemanager-schema should give you that)
- Apply the upgrade procedure as if you were migrating from 4.0.1 (Leap 42.3)
to 4.0.2 (Leap 15.1) 
- This will create a log at /var/log/spacewalk/schema-upgrade where you will
see lines like "SQL> select 'susemanager-schema-3.2.18-to-susemanager-
schema-3.2.19/002-alter-susesaltevent.sql.postgresql' from dual;" for each SQL
- Take note of the susemanager-schema version installed by the update (should
be 4.0.13, use the same command on the first step)
- Then review /etc/sysconfig/rhn/schema-upgrade/ and verify if everything from
the migration path from current_version up to 4.0.13 was applied.
If something is missing, you will need to apply it manually:
$ sudo su - postgres
$ psql -f <SQL_SCRIPT> <yourdbname-usually-uyuni>
But of course, I have to repeat it: it is not supported in any way and could
bring problems in the future.
So the preferred and only supported method is starting from scratch with 4.0.2
and then readding the minions.
 If you see errors about lines 35-38 with rpm being unable of removing
server-migrator.sh), that should be fine.
On viernes, 2 de agosto de 2019 18:29:54 (CEST) Cristian Gherman wrote:
First of all, I love you work. It helped me very much in last months.
I have Uyuni server on Opensuse 15.0 which used devel repos until
Opensuse 15.1 switch.
I look over documentation andnot found how to upgrade OS and Uyuni
whitout loose minion settings (or readd to the master).
What you suggest to do:
a) Clean install and reattach minions to the new master?
b) backup salt master config files, postgresql database, and restore on
new machine, after ?
c) Upgrade OS and Uyuni whithout any changes?
Thank you in advance for any replay.
Julio González Gil
Release Engineer, SUSE Manager and Uyuni