What should I look for when troubleshooting a "Connection refused or timed out" when checking via NRPE to a Linux machine? I'm having this problem on two targets. So far, I've installed NRPE on 5 machines, and 3 worked without a hitch, and these two are giving me headaches. Some info about the targets. 10.5.10.50 is my Nagios server, dfslit1 10.5.10.90 is the target client, dfslrdb01. The second problem machine produces identical output to this one, aside from a different CentOS version. Both (well, all 5) are running this version of NRPE: NRPE - Nagios Remote Plugin Executor Copyright (c) 1999-2008 Ethan Galstad (<a href="mailto:nagios@nagios.org">nagios@nagios.org</a>) Version: 2.12 Client OS versions are: CentOS release 5.3 (Final) CentOS release 5.2 (Final) From /var/log/messages when I restart the NRPE: Aug 19 13:51:08 dfslrdb01 nrpe[13249]: Starting up daemon Aug 19 13:51:08 dfslrdb01 nrpe[13249]: Listening for connections on port 5666 Aug 19 13:51:08 dfslrdb01 nrpe[13249]: Allowing connections from: 127.0.0.1,10.5.10.50 Aug 19 13:51:53 dfslrdb01 nrpe[13249]: Caught SIGTERM - shutting down... Aug 19 13:51:53 dfslrdb01 nrpe[13249]: Cannot remove pidfile '/var/run/nrpe.pid' - check your privileges. Aug 19 13:51:53 dfslrdb01 nrpe[13249]: Daemon shutdown Aug 19 13:51:53 dfslrdb01 nrpe[13266]: Starting up daemon Aug 19 13:51:53 dfslrdb01 nrpe[13266]: Listening for connections on port 5666 Aug 19 13:51:53 dfslrdb01 nrpe[13266]: Allowing connections from: 127.0.0.1,10.5.10.50 (10.5.10.50 is my Nagios server) I look in /var/run/nrpe.pid and the file is gone when NRPE stops, and is re-created when it starts. When it's running, permissions are: [root@dfslrdb01 ~]# ll /var/run/nrpe.pid -rw-r--r-- 1 root root 6 Aug 19 14:09 /var/run/nrpe.pid Checking to see if the port's open: [mikes@dfslrdb01 ~]$ netstat -l | grep 5666 tcp 0 0 *:5666 *:* LISTEN Command definition from /etc/nagios/nrpe.cfg: command[check_disk]=/usr/lib64/nagios/plugins/check_disk -w 20% -c 10% -p /dev/sda1 Running the command on the target machine: [mikes@dfslrdb01 ~]$ sudo su - nagios -sh-3.2$ /usr/lib64/nagios/plugins/check_disk -w 20% -c 10% -p /dev/sda1 DISK OK - free space: / 294574 MB (45% inode=99%);| /=358494MB;550890;619751;0;688613 Running it at the command line from the server; result is the same with or without -n: nagios@dfslit1:~$ /usr/lib/nagios/plugins/check_nrpe -H 10.5.10.90 -c check_disk Connection refused or timed out nagios@dfslit1:~$ tcptraceroute 10.5.10.90 5666 Selected device eth0, address 10.5.10.50, port 36013 for outgoing packets Tracing the path to 10.5.10.90 on TCP port 5666, 30 hops max 1 10.5.10.90 2.965 ms !C 0.841 ms !C 0.744 ms !C nagios@dfslit1:~$ telnet 10.5.10.90 5666 Trying 10.5.10.90... telnet: Unable to connect to remote host: No route to host I installed from Dag's repository: <a href="http://dag.wieers.com/rpm/FAQ.php#B">http://dag.wieers.com/rpm/FAQ.php#B</a> [root@dfslrdb01 ~]# iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination RH-Firewall-1-INPUT all -- anywhere anywhere Chain FORWARD (policy ACCEPT) target prot opt source destination RH-Firewall-1-INPUT all -- anywhere anywhere Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain RH-Firewall-1-INPUT (2 references) target prot opt source destination ACCEPT all -- anywhere anywhere ACCEPT icmp -- anywhere anywhere icmp any ACCEPT esp -- anywhere anywhere ACCEPT ah -- anywhere anywhere ACCEPT udp -- anywhere 224.0.0.251 udp dpt:mdns ACCEPT udp -- anywhere anywhere udp dpt:ipp ACCEPT tcp -- anywhere anywhere tcp dpt:ipp ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:smtp ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:nfs ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:https ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:http ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:sunrpc ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:terabase ACCEPT udp -- anywhere anywhere state NEW udp dpt:terabase ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:newoak ACCEPT udp -- anywhere anywhere state NEW udp dpt:newoak ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:pxc-spvr-ft ACCEPT udp -- anywhere anywhere state NEW udp dpt:pxc-spvr-ft ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:rquotad ACCEPT udp -- anywhere anywhere state NEW udp dpt:rquotad ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:mysql REJECT all -- anywhere anywhere reject-with icmp-host-prohibited My problem seems similar to this, but neither my nor Google Translate's German is good enough to figure out what fixed the problem. Perhaps it's in suiss-allemagne, but high school French is doing me no good today. <a href="http://www.nagios-portal.org/wbb/index.php?page=Thread&threadID=12885">http://www.nagios-portal.org/wbb/index.php?page=Thread&threadID=12885</a> What should I look at next? Thanks, -Mike