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Debugging Bandwidth Performance Graphs in Nagios – How we do it

by | Dec 26, 2020

Debugging bandwidth performance graphs in Nagios can be done easily for graphs that are missing or the ones that do not show any performance data.

debugging bandwidth performance graphs nagios

At Bobcares, we get requests to fix this issue from our customers who use Nagios as the monitoring tool.

Today let’s see how our Support Engineers fix this issue with ease as a part of our Server Management Services.

What are the common causes?

Before going to the steps of debugging bandwidth performance graphs in Nagios let’s see what are the common causes.

Some causes commonly seen are listed below:

1. Cron daemon not running
2. Corrupt configuration files
3.  Deprecated MRTG config files causing MTRG to run longer than five minutes
4. No proper file/folder permissions
5. MRTG config files logging errors
6. MTRG running longer than five minutes
7. Command not executing correctly
8.  Directory Missing
9. SNMP Configuration Incorrect

 

How to debug bandwidth performance graphs in Nagios?

Let’s see how debugging bandwidth performance graphs in Nagios is done by our Support Techs.

1. Cron Daemon

We must ensure that the cron daemon is running.

We can check this by running the following command:

RHEL 6|CentOS 6|Oracle Linux 6

# service crond status

 

RHEL 7|CentOS 7|Oracle Linux 7

# systemctl status crond.service

 

Ubuntu 14|Debian|Ubuntu 16/18

# service cron status/pre>
# systemctl status cron.service

 

If the corn daemon is not running, we can start it by running the following command:

RHEL 6|CentOS 6|Oracle Linux 6

# service crond start

 

RHEL 7|CentOS 7|Oracle Linux 7

# systemctl start crond.service

 

Ubuntu 14

# service cron start

 

Debian|Ubuntu 16/18

# systemctl start cron.service

[Need assistance? We can help you!]

 

2. Corrupt Files/Deprecated Files

Corrupt files could be caused by an unexpected shutdown of the server or if the server’s drive has filled up and could not save the current bandwidth data.

The configuration files are in /etc/mrtg/conf.d/

To troubleshoot the corrupt files, run the following command and if any errors are displayed, resolve the errors, and re-run the command.

# LANG=C LC_ALL=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg

Running the previous command should highlight any devices that are timing out. Simply delete the config files using the following command:

# rm -f /etc/mrtg/conf.d/196.X.X.X.cfg

We must put the IP address after /conf.d/

 

3. File/Folder Permissions

Generally, the performance data files are stored in 2 locations on the XI server.

The first folder is /var/lib/mrtg

This is where the Bandwidth graphs are stored. Here is a sample of what the permissions look like.

-rw-rw-r-- 1 apache nagios 105312 Jan 27 13:25 192.168.5.43_71.rrd
-rw-rw-r-- 1 apache nagios 105312 Jan 27 13:25 192.168.5.43_72.rrd
-rw-rw-r-- 1 apache nagios 105312 Jan 27 13:25 192.168.5.43_73.rrd
-rw-rw-r-- 1 apache nagios 105312 Jan 27 13:25 192.168.5.43_74.rrd
-rw-rw-r-- 1 apache nagios 0 Jan 27 13:25 mrtg.ok

 

To reset the permissions on the folders and files in /var/lib/mrtg, we can execute the following commands:

RHEL|CentOS|Oracle Linux

# cd /var/lib/mrtg
# chown apache:nagios *
# chmod 0664 *

Debian|Ubuntu

# cd /var/lib/mrtg
# chown www-data:nagios *
# chmod 0664 *

The second folder is at this location:
/usr/local/nagios/share/perfdata

This is where the performance data for all the hosts and services are stored. Here is a sample of what the permissions look like:

drwxrwxr-x 2 nagios nagios 4096 Jan 15 11:29 192.168.1.1
drwxrwxr-x 2 nagios nagios 4096 Jan 27 13:30 192.168.5.43

The permissions of the folder 196.XX.Xlook like this:

-rw-rw-r-- 1 nagios nagios 1534768 Nov 29 13:42 _HOST_.rrd
-rw-rw-r-- 1 nagios nagios 3892 Nov 29 13:42 _HOST_.xml

To reset the permissions on the folders and files in /usr/local/nagios/share/perfdata, execute the following commands:

# cd /usr/local/nagios/share/perfdata
# for folder in `find . -type d`; do chown -R nagios:nagios $folder; done
# for folder in `find . -type d`; do chmod 0775 $folder; done
# for folder in `find . -type d`; do chmod 0664 $folder/*; done

[Still facing issue? We can help you!]

4. MRTG Config Files Logging Errors

If MRTG faces issue in collecting data from a device, it will log this in the root mailbox.

When a mailbox is not checked regularly it will increase the size and thus slow down MRTG.

To identify any  MRTG port having problems, we execute the below command in a terminal session:

# LANG=C LC_ALL=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg

We will get the ports with errors in the output.

We can comment out these ports in the relevant config files by using a hash #. Each port in the config file is 37 lines long, you need to comment out all 37 lines.

 

5. MRTG Running Longer Than Five Minutes

When MRTG runs it is considered to get complete within five minutes.

If it is still running the next time it runs at the five-minute interval, it will terminate as there is already an MRTG job running.

This means data is not collected from devices at this interval.

We can identify how long it takes for MRTG to run by executing the following command:

# time LANG=C LC_ALL=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg

The output will end with how long the command took to execute.

We can increase the number of forks MRTG is allowed to spawn when it executes to fix this.

In /etc/mrtg/mrtg.cfg as per the following directive:

Forks: 4

Increase the number as required.

 

6. Command Not Executing Correctly

Try running the command that Nagios XI runs to check the status of a device. Nagios XI uses the check_rrdtraf plugin.

Test running this plugin manually by running a check, similar to the following:

# /usr/local/nagios/libexec/check_rrdtraf -f '/var/lib/mrtg/196.X.X.X_1.rrd' -w 1 -c 2

It will return:

OK - Current BW in: 1.57Kbps Out: 365.41bps|in=1.573002Kb/s;1;2 out=365.413424b/s;1;2

[Still facing issue? We can help you!]

 

7. Directory Missing

Make sure the /var/lock/mrtg/ directory exists.

We can check the /var/spool/mail/root mailbox using this command:

# grep templock /var/spool/mail/root

If we get the following error then we have to recreate the /var/lock/mrtg/  folder.

2016-10-03 19:45:02: ERROR: Creating templock /var/lock/mrtg/mrtg_l_5612: No such file or directory at /usr/bin/mrtg line 1961

To recreate the folder using the following command:

# mkdir /var/lock/mrtg

 

8. SNMP Configuration Incorrect

Older versions of the Switch Wizard called MRTG with arguments for SNMPv2c, which MRTG does not use.

Generally, the entries look like this:

Target[www.hostaddress.com]: 1:SNMP_Community_String@www.hostaddress.com:::::2

[Need assistance? We can help you!]

Conclusion

In short, saw various methods that our Support Engineers use for debugging bandwidth performance graphs Nagios.

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