Took me a little bit to get back to this.
Performed some testing from the CLI on the cmk server and host.
DNS is resolving properly between the two hosts.
A telnet from the cmk server to the host port 6556 successfully retrieves the agent info’
OMD[corpnms]:~$ cmk -d web03-2.prod.corporate.local
<<<check_mk>>>
Version: 2.0.0p18
AgentOS: linux
Hostname: web03-2
<snip>
A telnet from the host to the cmk server to port 80/443 is also successful.
[root@web03-2 ~]# telnet corpnms01.corporate.local 80
Trying 192.168.44.93...
Connected to corpnms01.corporate.local.
Escape character is '^]'.
^]
[root@web03-2 ~]# telnet corpnms01.corporate.local 443
Trying 192.168.44.93...
Connected to corpnms01.corporate.local.
Escape character is '^]'.
^]
Manual registration from the host showed the same results as the earlier log entries.
Going to register agent at deployment server
Unexpected answer from Checkmk server: Missing json data. Maybe we are talking to an agent bakery from before Checkmk 2.0 ?
See syslog or Logfile at /var/lib/check_mk_agent/cmk-update-agent.log for details.
I performed an update to the CMK Server to release 2.0.0p26.cme, baked and signed the agent and retried registration.
No difference.
With the missing attribute and reference to earlier releases, I deleted the host from check_mk completely, committed the changes and then added it back.
Registration still failed.
Finally, I removed the agent again, deleted the /etc/cmk-update-agent.state file and related /var/lib/check_mk folder.
Downloaded the updated agent 2.0.0p26 version and installed. Manual registration was finally successful.
Going to register agent at deployment server
Successfully registered agent of host "web03-2.prod.corporate.local" for deployment.
You can now update your agent by running 'cmk-update-agent -v'
Saved your registration settings to /etc/cmk-update-agent.state.
So honestly unable to isolate what was causing it to fail but the:
- Update of the checkmk server release
- 2nd round of agent removal/install
allowed it to register.
Hope this helps someone else.