Werk #22166: Agent controller: Checkmk 2.1 controllers can no longer register
| Component | Checks & agents | ||
| Title | Agent controller: Checkmk 2.1 controllers can no longer register | ||
| Date | Oct 15, 2026 | ||
| Level | Trivial Change | ||
| Class | New Feature | ||
| Compatibility | Incompatible - Manual interaction might be required | ||
| Checkmk versions & editions |
|
An agent controller of Checkmk 2.1 can no longer register with the site.
The agent receiver no longer offers the endpoints /pairing and
/register_with_hostname, which this controller uses for its registration.
Agent controllers of Checkmk 2.2 and later register through other endpoints.
They are not affected.
A registration attempt of an agent controller of Checkmk 2.1 now fails with
the HTTP status 404 Not Found. The permission Agent pairing is removed as
well. User roles that still grant it keep working.
The removal does not affect the data transfer of hosts that an agent controller of Checkmk 2.1 registered earlier. However, this controller cannot renew its certificate. The controller therefore can't replace a certificate that has expired or that Checkmk 3.0 rejects (see Werk #20075). Up to now, the controller could register again in such a case. A new registration is no longer possible.
Update the agent on all hosts that still run an agent controller of Checkmk 2.1. The current agent controller takes over the existing connections. It also renews the certificates of these connections.