NRPE Check Returning “Connection Refused” After Recent Server Update

[PolyTrackk]

Hi everyone,

I’m running into an issue with NRPE after updating one of my Linux servers (Ubuntu 22.04). Before the update, all remote checks from my Nagios server were working fine, but now I’m consistently getting a “Connection refused” error when trying to run checks on this host.

I’ve verified that the NRPE service is running, and I can see it listening on port 5666 using netstat. I also double-checked the allowed_hosts setting in nrpe.cfg, and my Nagios server’s IP is definitely listed there. Firewall-wise, I’ve temporarily disabled UFW just to test, but the issue still persists.

From the Nagios server side, I’m using the check_nrpe command, and it times out or fails immediately with connection refused. I’m wondering if the update may have changed something related to SSL/TLS requirements or if there’s a compatibility issue with the NRPE version.

Has anyone run into something similar after a system update? Any suggestions on what logs or configs I should be checking next would really help.

Thanks in advance!

[ekapsner]

Hello,

When troubleshooting NRPE, it is often helpful to edit the NRPE config file and change debug=0 to debug=1. After restarting NRPE, this will add more debugging information to the log files. Unless otherwise specified in nrpe.cfg, any logs will be written to syslog.

What version of NRPE is on the Ubuntu server and what version of check_nrpe is being used?

-Emmett