Thx, for your answer, you are right. It was the REST API Documentation in the “Misc”-Section of the Add-Ons in Paper UI. But I hadn’t installed before Upgrade, so I don’t know what to do with it.
And I have to say that I do not know what the REST API is for, as I never used it or had to use 
I’m a bit dump 
, but always willing to learn 
. Do you have some hints for me, of course if you want, also by PM ?
Cheers - Peter
The REST API is how the UIs like PaperUI and BasicUI communicate with the OH core to give you the ability to interact with OH. So if you wanted to build your own UI or if you want to interact with just one part of OH (e.g. send a command to an Item from an external application, enable/disable a Thing from OH Rules or an external application, you would use the REST API.
As mentioned earlier, the REST API Documentation is just that, documentation. Though one of the nice things about it is that it is interactive documentation. You can actually issue commands to OH through the documentation. I find it handy for some adhoc testing of Rules and such as I can change Things and Items right there from the documentation.
Thx, Rich, and of course Udo, for your help and hints. I will install it again (the REST API Doc ) and try to find out, what can I do with it.
Cheers,
Peter
Sometimes it’s hard to get a no-openhab-binding-system bound to openhab, a nice option is to send API calls to openHAB (no polling…) I’ve used this method to get telephone numbers from my Asterisk to openHAB, it’s a very simple AGI script which is executed at every phone call.
How did you downgrade your openhab installation?
I also had 2.5 M1 installed (on my raspi openhabian) and wanted to get back to stable 2.4.
Unfortunately, the downgrade did not work. I recorded a backup to 2.4.
You need to switch your repository back to stable. The milestone builds are on the testing repo:
Then check this post:
Hi Stefan,
i’m still dealing with the 2.5.M1 Version, but for me it’s very easy to go back, as i made an image of my SD-Card from time to time, and naturally before an upgrade. I have 3 SD-Cards ( tested that the image fits to it), so I have no problems in case of crash or to restore an older version. It’s only the work you’ve done between the changes, but mostly they won’t work on the elder Release, cause they were the reason for the Upgrade.
Cheers,
Peter
THX
To explain it in more detail. What I did:
open ssh -> sudo openhabian-config
Point 40 openHAB releated
switched back from openHAB tesing to 41 openHAB release
Update and Upgrade System.
But it did not work. 
Luckily I create a backup every day and could go back to 2.4.
Afterwards I only exchanged the DB files and finished.
Sorry, no idea about openHABian, never used it.
Define “did not work”. OH wouldn’t start? Parts of OH stopped working? It didn’t change the version back to the release?
I’m pretty sure you will have to purge the old package manually. So
sudo apt remove openhab2
sudo apt purge openhab2
But I did not test this, so this is just a guess.
I thought the downgrade did not work.
After the completed actions, 2.5 M1 was still installed and running.
@Udo_Hartmann THX for the hint. Perhaps I try it in the future 
When is the 2.5.0.M2 output expected?
When are the builds working again?
I’m sure there will be an announcement. David predicted another 60 days.
Isn´t openhab 2.5 (release version) suppose to be released in May/June?
I doubt they will be able to stick to the regular release cycle for this next release. The changes involved with remerging ESH into the OH baseline and changing the build system are extensive. But I don’t know anything more than you do about what is in the maintainer’s goals.
We are also actively pushing java11 support now.
But at the moment it really looks like openhab1 add-ons will not be part of any future release is my prediction.
Which of course doesn’t stop someone to just use the current version.
Wow. Wasn’t this subject of the “big OH3 direction” discussion? I’m a bit surprised to see this as an expectation already for OH2.5…