Starting with Checkmk 2.3.0, the Checkmk server won't be able to communicate with an Agent Updater of version 1.6.0 or lower.
The reason for this is that starting with Checkmk 2.0.0, the internal protocol for updating agents has changed.
While we have maintained the old protocol up to and including Checkmk 2.2.0, we are now finally deprecating it as of Checkmk 2.3.0.
As a consequence, an Agent Updater v1.6.0 or lower won't be able to either register or update agents anymore, neither automatically, nor manually.
Please make sure to update all installed agent packages on all hosts to at least v2.0.0 before upgrading the Checkmk server to Checkmk 2.3.0.
Note: The Checkmk agent package, including the agent updater if it is configured, will be given the same version as the Checkmk site on which it was baked.
It is therefore sufficient to update agents (automatically or manually) with an active Checkmk 2.0.0, 2.1.0 or 2.2.0 server installed.
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