NRPE: Unable to read output

[Pratapa]

Hi,

We have configured Service check "Network Traffic" in one of the client machines.

But we are getting error while invoking from command prompt from Nagios server.

[root@nagios libexec]# ./check_nrpe -H host1 -c check_iftraffic
NRPE: Unable to read output

[root@nagios libexec]# ./check_nrpe -H host1
NRPE v3.2.1

Following is the entry in nrpe.cfg file on client's machine host1.

command[check_iftraffic]=/usr/lib64/nagios/plugins/ce/check_iftraffic_nrpe.pl -i eth0 -b 10000 -u m -w 85 -c 95


Following are the permissions of the file.

[root@host1 ce]# ls -l /usr/lib64/nagios/plugins/ce/check_iftraffic_nrpe.pl
-rwxr-xr-x. 1 root root 7806 Feb 14 17:22 /usr/lib64/nagios/plugins/ce/check_iftraffic_nrpe.pl

When we execute at command prompt, it is getting executed fine.

[root@host1 ce]# /usr/lib64/nagios/plugins/ce/check_iftraffic_nrpe.pl -i eth0 -b 10000 -u m -w 85 -c 95
Total RX Bytes: 1461785.40 MB, Total TX Bytes: 0.01 MB<br>Average Traffic: 31.10 kB/s (0.0%) in, 0.00 kB/s (0.0%) out| inUsage=0.0;85;95 outUsage=0.0;85;95 inBandwidth=31.10 outBandwidth=0.00 inAbsolut=1532793087445 outAbsolut=7209


We verified directory permissions also, they are fine.

[root@host1 ce]# ls -ld .
drwxr-xr-x. 2 root root 170 Feb 14 17:22 .


What could be the problem.

[Pratapa]

Additional information :

[root@host1]# service nrpe status
Redirecting to /bin/systemctl status nrpe.service
● nrpe.service - Nagios Remote Program Executor
Loaded: loaded (/usr/lib/systemd/system/nrpe.service; disabled; vendor preset: disabled)
Active: active (running) since Fri 2020-02-14 20:16:18 AEDT; 30min ago
Docs: http://www.nagios.org/documentation
Process: 46177 ExecStopPost=/bin/rm -f /var/run/nrpe/nrpe.pid (code=exited, status=0/SUCCESS)
Main PID: 46179 (nrpe)
Tasks: 1
CGroup: /system.slice/nrpe.service
└─46179 /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -f

Feb 14 20:41:12 aeapsapwd01 nrpe[53420]: Warning: Could not set UID=995
Feb 14 20:44:21 aeapsapwd01 nrpe[54397]: Warning: Could not set effective GID=992
Feb 14 20:44:21 aeapsapwd01 nrpe[54397]: Warning: Unable to change supplementary groups using initgroups()
Feb 14 20:44:21 aeapsapwd01 nrpe[54397]: Warning: Could not set UID=995
Feb 14 20:44:56 aeapsapwd01 nrpe[54552]: Warning: Could not set effective GID=992
Feb 14 20:44:56 aeapsapwd01 nrpe[54552]: Warning: Unable to change supplementary groups using initgroups()
Feb 14 20:44:56 aeapsapwd01 nrpe[54552]: Warning: Could not set UID=995
Feb 14 20:46:11 aeapsapwd01 nrpe[54997]: Warning: Could not set effective GID=992
Feb 14 20:46:11 aeapsapwd01 nrpe[54997]: Warning: Unable to change supplementary groups using initgroups()
Feb 14 20:46:11 aeapsapwd01 nrpe[54997]: Warning: Could not set UID=995

[benjaminsmith]

Hi Pratapa,

The permissions on the plugin are root and cannot be run by the nagios user. You can confirum this by logging in as nagios su - nagios and testing.

Following are the permissions of the file.
[root@host1 ce]# ls -l /usr/lib64/nagios/plugins/ce/check_iftraffic_nrpe.pl
-rwxr-xr-x. 1 root root 7806 Feb 14 17:22 /usr/lib64/nagios/plugins/ce/check_iftraffic_nrpe.pl

Change to and let me know if the issue is resolved.

Code: Select all

chmod 755 /path/*
chown root:nagios /path/*

[Pratapa]

We changed the permissions but still did not work.

We did further troubleshooting.

We added following two entries and checked from Nagios server.

command[check_iftraffic]=/usr/lib64/nagios/plugins/check_iftraffic_nrpe.pl -i eth0 -b 10000 -u m -w 85 -c 95
command[check_users]=/usr/lib64/nagios/plugins/check_users -w 5 -c 10


From Nagios server.

[root@nagios server]# ./check_nrpe -H host1 -c check_users
USERS OK - 1 users currently logged in |users=1;5;10;0
[root@nagios server]# ./check_nrpe -H host1 -c check_iftraffic
NRPE: Unable to read output


[root@host1 plugins]# ls -l check_users
-rwxr-xr-x. 1 root root 45336 Nov 22 2017 check_users
[root@host1 plugins]# ls -l check_iftraffic_nrpe.pl
-rwxr-xr-x. 1 root root 7806 Feb 17 19:59 check_iftraffic_nrpe.pl


[root@host1 plugins]# /usr/lib64/nagios/plugins/check_iftraffic_nrpe.pl -i eth0 -b 10000 -u m -w 85 -c 95
Total RX Bytes: 1469947.37 MB, Total TX Bytes: 0.01 MB<br>Average Traffic: 30.85 kB/s (0.0%) in, 0.00 kB/s (0.0%) out| inUsage=0.0;85;95 outUsage=0.0;85;95 inBandwidth=30.85 outBandwidth=0.00 inAbsolut=1541351533341 outAbsolut=7209


check_users and check_iftraffice_nrpe.pl are having same permissions and ownership and both the plugins are in the same directory.

check_users is working but check_iftraffic_nrpe.pl is not working.

We see that nothing wrong with the script and nothing wrong with the permissions. But still we are not getting the expected output..

[Box293]

I googled that plugin and I found the following:

Code: Select all

# Path to  tmp files
my $TRAFFIC_FILE = "/tmp/traffic";

Does the nagios user have permission to write to this location?
A common issue is that a test is first done as a root user and the file created only has permissions for root. Then when nagios goes to run the nagios user doesn't have permission to that file.

[Pratapa]

[root@host1 ce]# cat check_iftraffic_nrpe.pl|grep tmp
# Path to tmp files
my $TRAFFIC_FILE = "/tmp/traffic";
[root@host1 ce]# pwd
/usr/lib64/nagios/plugins/ce
[root@host1 ce]# cd /tmp
[root@host1 tmp]# ls -ld .
drwxrwxrwt. 11 root root 12288 Feb 18 17:10 .
[root@host1 tmp]# ls -l traffic
ls: cannot access traffic: No such file or directory
[root@host1 tmp]# cd traffic
-bash: cd: traffic: No such file or directory
[root@host1 tmp]# pwd
/tmp
[root@host1 tmp]# ls -l traffic_ifeth0
-rw-r--r--. 1 root root 24 Feb 18 16:42 traffic_ifeth0

[scottwilkerson]

[root@host1 tmp]# ls -l traffic_ifeth0
-rw-r--r--. 1 root root 24 Feb 18 16:42 traffic_ifeth0

My guess is this is the file it is trying to read/write to and cannot as NRPE is going to be running as the nagios user. this could be because the file was first created when you ran it from the command line as root

Lets do the following

Code: Select all

chmod +w /tmp/traffic_ifeth0

then try again

[Pratapa]

Yes, we did that

[root@host1 tmp]# chmod 666 /tmp/traffic_ifeth0


It's resolved.

Thank you very much.

You may lock the thread.

[scottwilkerson]

Yes, we did that

[root@host1 tmp]# chmod 666 /tmp/traffic_ifeth0


It's resolved.

Thank you very much.

You may lock the thread.

Great!

Locking thread