Managing Nagios logs

Nagios natively supports log rotation, a functionality managed using log_rotation main configuration option. This is the configuration option description taken from official nagios documentation

Format: log_rotation_method=[n/h/d/w/m]
Example: log_rotation_method=d

This is the rotation method that you would like Nagios to use for your log file. Values are as follows:

n = None (don't rotate the log - this is the default)
h = Hourly (rotate the log at the top of each hour)
d = Daily (rotate the log at midnight each day)
w = Weekly (rotate the log at midnight on Saturday)
m = Monthly (rotate the log at midnight on the last day of the month)

Many times people become confused by the Nagios log management capabilities and believe that, besides rotating, Nagios will erase older files too... or well, some angel in our system will do for us. Saddly this is not real neither in Nagios nor in Centreon systems and older logs remain in our disk for months or even years.

This simple script can be very helpful in order to address the previous fact. It manages log files in two combinable ways: Compressing and or deleting files older than x days. It takes three arguments: 

• Directory where nagios logs are stored
• Age, in days, for files that will be compressed
• Age, in days, for files that will be deleted

For instance, and given that it is named as manage_naglogs, this example would delete files older than 30 days and would compress files older than 7 days:

manage_naglogs /var/log/nagios 7 30

And here comes the script:

#!/bin/bash

if [ $3 -gt 0 ]

then

        find $1/nagios-*.gz -mtime +$3 -exec rm {} \;

        find $1/nagios-*.log -mtime +$3 -exec rm {} \;

fi

if [ $2 -gt 0 ]

then

        find $1/nagios-*.log -mtime +$2 -exec gzip {} \;

fi

In order to run it periodically, I recommend adding the needed commands to cron. In systems like Debian where /etc/cron.daily stores scripts run every day, and assuming you have saved the previous script in /usr/local/nagios/bin, create an script like this, save it in /etc/cron.daily and set proper file permissions for being run for cron daemon (chmod 755 will do the job):

#!/bin/bash

/usr/local/nagios/bin/manage_naglogs /var/nagios/logs 7 30

In systems where only crontab is available, next entry will do the job. It will run our script once every day at 3:00am:

00 3 * * * root /usr/local/nagios/bin/manage_naglogs /var/nagios/log 7 30

Finally one advice for those using Centreon: Keep, at least, one nagios rotated log file untouched (ie, neither compressed nor deleted). Have in mind that centreon run every day (usually at 1:00am) an script for parsing Nagios log files in order to create availability reports. To achieve it, use values higher than 1 for the second and third script arguments.

Last but not least...

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