Collectd is a data collection tool for a large number of Unix based services. The output of collectd is in rrd format. You can use tools such as collectd-web to graph the output and view via Apache. In this article I will show you on how install collectd on CentOS and use it for monitoring libvirt (KVM) as well as for Apache monitoring. Collectd does not do any alerting, just trend analysis, similar to MRTG or Cacti. Collectd is not a replacement for Nagios, which does alerting as well.

Install collectd

yum install collectd -y
yum install collectd-virt -y
yum install collectd-apache -y

In /etc/collectd.conf replace:

PluginDir   "/usr/lib/collectd"


PluginDir   "/usr/lib64/collectd"

In /etc/collectd.conf uncomment the following lines, while replacing BaseDir with the location you want the rrd output files to go to

BaseDir     "/usr/var/lib/collectd"
PIDFile     "/usr/var/run/"
PluginDir   "/usr/lib64/collectd"
LoadPlugin logfile

        LogLevel info
        File "/var/log/collectd.log"
        Timestamp true
        PrintSeverity false

Also uncomment the following to load apache and libvirt plugins:

LoadPlugin apache
LoadPlugin libvirt

        Connection "kvm:///"
        RefreshInterval 60
#       Domain "name"
#       BlockDevice "name:device"
#       InterfaceDevice "name:device"
#       IgnoreSelected false
#       HostnameFormat name

Start collectd

/etc/init.d/collectd start

One way to view collectd stats is to use Apache with collectd-web.

Install collectd-web:

yum install collectd-web -y

Edit the collections file:

vim /etc/collections.conf
Change DataDir to be:
DataDir "/var/log/collectd/"

Also, rewrite HTTP to HTTPS for security:

Redirect HTTP to HTTPS:
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}

Point your browser to http://localhost/collectd


Nagios comes in two flavors, a commercial version and an open source free version. In this blog I will cover the basics of installing and setting Nagios up.

Download Nagios:

sudo wget
sudo wget

Install the needed development libraries:

sudo yum install -y wget httpd php gcc glibc glibc-common gd gd-devel make net-snmp  openssl-devel

Untar and build Nagios:

tar zxvf nagios-4.0.0rc1.tar.gz
tar zxvf nagios-plugins-1.4.16.tar.gz
cd nagios
./configure --with-command-group=nagcmd
make all
make install
make install-init
make install-config
make install-commandmode
make install-webconf

Set proper permission and verify if the config file is ok:

cp -R contrib/eventhandlers/ /usr/local/nagios/libexec/
chown -R nagios:nagios /usr/local/nagios/libexec/eventhandlers
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Make sure you disable SELINUX, otherwise Nagios won’t work:

echo 1 > /selinux/enforce
sed -e 's/SELINUX=enforcing/SELINUX=disabled/' /etc/selinux/config  > /etc/selinux/
mv /etc/selinux/ /etc/selinux/config

Configure Nagios plugins:

cd ../nagios-plugins-1.4.15
./configure --with-nagios-user=nagios --with-nagios-group=nagios
make install

Now you are ready to start Nagios:

/etc/init.d/nagios start
/etc/init.d/httpd start
chkconfig --add nagios
chkconfig --add httpd
chkconfig --level 3 nagios on
chkconfig --level 3 httpd on

Create Nagios web user:

htpasswd –c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Now you are ready to view: http://yourhost/nagios. Login with nagiosadmin as the user and the password you specified with htpasswd.
Next thing to do is configure the hosts you want to monitor. I normally uncomment the line cfg_dir=/usr/local/nagios/etc/servers in /usr/local/nagios/etc/nagios.cfg and put my server configs there. If you need assistance in creating a config file view additional documentation here

Cacti is a very useful tool for graphing SNMP based data. If you have used MRTG, Cacti is MRTG on steroids. In this article I will cover the basics of installing Cacti. Some of the things you can graph with Cacti include load average, memory usage, and disk usage.

Install Apache

sudo yum install httpd httpd-devel -y

Install MySQL

sudo yum install mysql mysql-server

Install PHP

sudo yum install php-mysql php-pear php-common php-gd php-devel php php-mbstring php-cli php-mysql -y

Install PHP-SNMP

sudo yum install php-snmp -y

Install Net-SNMP

sudo yum install net-snmp-utils net-snmp-libs -y


sudo yum install rrdtool

Enable EPEL repository in order to download and install cacti

sudo wget
sudo rpm -ivh epel-release-6-8.noarch.rpm

Download and install Cacti

sudo yum install cacti

Start MySQL, HTTPD, and SNMP

sudo service httpd start
sudo service mysqld start
sudo service snmpd start

Ensure that all 3 services start upon system boot

sudo /sbin/chkconfig --levels 345 httpd on
sudo /sbin/chkconfig --levels 345 mysqld on
sudo /sbin/chkconfig --levels 345 snmpd on

Create MySQL Cacti database

mysql -u root -p
mysql> create database cacti;
mysql> GRANT ALL ON cacti.* TO cacti@localhost IDENTIFIED BY 'your-password-here';
mysql> FLUSH privileges;
mysql> quit;

Create the tables in the Cacti database

rpm -ql cacti | grep cacti.sql
mysql -u cacti -p cacti < /usr/share/doc/cacti-0.8.8a/cacti.sql

Configure database connection values:

sudo vi /etc/cacti/db.php
/* make sure these values reflect your actual database/host/user/password */
$database_type = "mysql";
$database_default = "cacti";
$database_hostname = "localhost";
$database_username = "cacti";
$database_password = "your-password-here";
$database_port = "3306";
$database_ssl = false;

Configure Cacti in Apache

sudo vi /etc/httpd/conf.d/cacti.conf
Alias /cacti    /usr/share/cacti

        Order Deny,Allow
        Deny from all
        Allow from 

Restart Apache

sudo /etc/init.d/httpd restart

Add Cacti to cron

sudo vi /etc/cron.d/cacti

#Uncomment the following line
*/5 * * * *    cacti   /usr/bin/php /usr/share/cacti/poller.php > /dev/null 2>&1

Next step is to install SNMPD on clients so that Cacti can poll the host, in the below example I am using Ubuntu client

sudo apt-get install snmpd
sudo apt-get install snmp-mibs-downloader

Enable SNMPD to listen on all interfaces on the Ubuntu client:

sudo vi /etc/default/snmpd
#Comment out the below line
SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -g snmp -I -smux -p /var/run/'
#Add the below line
SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/ -c /etc/snmp/snmpd.conf'

Replace /etc/snmp/snmpd.conf with the following on the Ubuntu client:

$ cat /etc/snmp/snmpd.conf
rocommunity public
syslocation "Your Location"

iquerySecName   internalUser
rouser          internalUser

On the client restart snmpd:

sudo /etc/init.d/snnmpd stop
sudo /etc/init.d/snnmpd start

You are now ready to access Cacti with the URL of your host:


At the Installer screen click on ‘Next’ and ‘Next’. Cacti will show you the path of rrdtool and other binaries, if they look ok, accept and click on Finish. For user login use admin as username and password as admin. You will have to select a new password after which you are ready to add hosts. For additional reference see

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