I am running OH 2.2 release build. Can it even happen that bindings will be updated for this release (for example to fix a bug), or do I need to be on snapshot/nightly (or something similar) to receive such updates?
If bindings are in deed updated for the release build, how do I know if I am running the latest version?
And if I know that an update is available, how to I replace my current binding with the new one?
If you get hold of an updated binding (jar), you simply drop it in the addons folder. Then you go to Karaf to stop/uninstall the current binding and start the new. To see the version of the binding do a list command in Karaf.
Starting with version 2.2, certain sever bugs that are fixed will be backported to the 2.2 release. When that occurs there will be a 2.2.1 release and when you run apt-get upgrade you will get the release. This can include bug fixes to the core or to individual bindings. But the versions will all work in lock step (i.e. if you install 2.2.1 release you will have 2.2.1 version bindings).
Sometimes it is possible to download and manually install a later binding version and run it on an older OH core (e.g. run a 2.3 snapshot on a 2.2 release). You would follow the process outlined by Martin. However, this is not guaranteed to always work as sometimes there are breaking changes made to the core that the newer bindings have to support which makes them no longer backwards compatible.
If you are experiencing a bug in a binding or need a new feature probably the easiest thing to do is upgrade your entire OH to the latest SNAPSHOT. Second would be to download and install the jar file manually.
To know when you might want to do that I recommend the following:
if you don’t have any problems, don’t upgrade individual bindings
if you have a show stopper problem with a binding, look in the GitHub repo for (openhab1-addons or openhab2-addons depending on what type of binding it is) to see if there is an issue for the problem. If there is you can subscribe to it and follow the discussion and discover when the problem gets fixed. If has already been fixed you can upgrade 24 hours after the fix was merged.