CentOS 7 install Nagios
This is from https://www.digitalocean.com/community/tutorials/how-to-install-nagios-4-and-monitor-your-servers-on-centos-7
Prerequisites
To follow this tutorial, you must
have superuser privileges on the CentOS 7 server that will run Nagios. Ideally,
you will be using a non-root user with superuser privileges. If you need help
setting that up, follow the steps 1 through 3 in this tutorial: Initial Server Setup with CentOS 7.
A LAMP stack is also required.
Follow this tutorial if you need to set that up: How To Install LAMP stack On CentOS 7.
This tutorial assumes that your
server has private networking enabled. If it doesn't, just replace all the
references to private IP addresses with public IP addresses.
Now that we have the prerequisites
sorted out, let's move on to getting Nagios 4 installed.
Install
Nagios 4
This section will cover how to
install Nagios 4 on your monitoring server. You only need to complete this
section once.
Install
Build Dependencies
Because we are building Nagios Core
from source, we must install a few development libraries that will allow us to
complete the build.
First, install the required
packages:
sudo
yum install gcc glibc glibc-common gd gd-devel make net-snmp openssl-devel
xinetd unzip
Create
Nagios User and Group
We must create a user and group that
will run the Nagios process. Create a "nagios" user and
"nagcmd" group, then add the user to the group with these commands:
sudo
useradd nagios
sudo
groupadd nagcmd
sudo
usermod -a -G nagcmd nagios
Let's install Nagios now.
Install
Nagios Core
Download the source code for the latest
stable release of Nagios Core. Go to the Nagios downloads page, and click the Skip to
download link below the form. Copy the link address for the latest stable
release so you can download it to your Nagios server.
At the time of this writing, the
latest stable release is Nagios 4.1.1. Download it to your home directory with
curl:
cd
~
curl
-L -O https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.1.1.tar.gz
Extract the Nagios archive with this
command:
tar
xvf nagios-*.tar.gz
Then change to the extracted
directory:
cd
nagios-*
Before building Nagios, we must
configure it with this command:
./configure
--with-command-group=nagcmd
Now compile Nagios with this
command:
make
all
Now we can run these make commands
to install Nagios, init scripts, and sample configuration files:
sudo
make install
sudo
make install-commandmode
sudo
make install-init
sudo
make install-config
sudo
make install-webconf
In order to issue external commands
via the web interface to Nagios, we must add the web server user, apache, to the nagcmd group:
·
sudo usermod -G nagcmd apache
·
Install
Nagios Plugins
Find the latest release of Nagios
Plugins here: Nagios Plugins Download. Copy the link address
for the latest version, and copy the link address so you can download it to
your Nagios server.
At the time of this writing, the
latest version is Nagios Plugins 2.1.1. Download it to your home directory with
curl:
cd
~
curl
-L -O http://nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz
Extract Nagios Plugins archive with
this command:
tar
xvf nagios-plugins-*.tar.gz
Then change to the extracted
directory:
cd
nagios-plugins-*
Before building Nagios Plugins, we
must configure it. Use this command:
./configure
--with-nagios-user=nagios --with-nagios-group=nagios --with-openssl
Now compile Nagios Plugins with this
command:
make
Then install it with this command:
sudo
make install
Install
NRPE
Find the source code for the latest
stable release of NRPE at the NRPE downloads page. Download the latest version
to your Nagios server.
At the time of this writing, the
latest release is 2.15. Download it to your home directory with curl:
·
cd ~
·
·
curl -L -O
http://downloads.sourceforge.net/project/nagios/nrpe-2.x/nrpe-2.15/nrpe-2.15.tar.gz
·
Extract the NRPE archive with this
command:
·
tar xvf nrpe-*.tar.gz
·
Then change to the extracted
directory:
·
cd nrpe-*
·
Configure NRPE with these commands:
·
./configure --enable-command-args
--with-nagios-user=nagios --with-nagios-group=nagios
--with-ssl=/usr/bin/openssl --with-ssl-lib=/usr/lib/x86_64-linux-gnu
·
Now build and install NRPE and its
xinetd startup script with these commands:
·
make all
·
·
sudo make install
·
·
sudo make install-xinetd
·
·
sudo make install-daemon-config
·
Open the xinetd startup script in an
editor:
·
sudo vi /etc/xinetd.d/nrpe
·
Modify the only_from line by adding the private IP address of the your Nagios
server to the end (substitute in the actual IP address of your server):
only_from
= 127.0.0.1 10.132.224.168
Save and exit. Only the Nagios
server will be allowed to communicate with NRPE.
Restart the xinetd service to start
NRPE:
·
sudo service xinetd restart
·
Now that Nagios 4 is installed, we
need to configure it.
Configure
Nagios
Now let's perform the initial Nagios
configuration. You only need to perform this section once, on your Nagios server.
Organize
Nagios Configuration
Open the main Nagios configuration
file in your favorite text editor. We'll use vi to edit the file:
sudo
vi /usr/local/nagios/etc/nagios.cfg
Now find an uncomment this line by
deleting the #:
#cfg_dir=/usr/local/nagios/etc/servers
Save and exit.
Now create the directory that will
store the configuration file for each server that you will monitor:
sudo
mkdir /usr/local/nagios/etc/servers
Configure
Nagios Contacts
Open the Nagios contacts
configuration in your favorite text editor. We'll use vi to edit the file:
sudo
vi /usr/local/nagios/etc/objects/contacts.cfg
Find the email directive, and
replace its value (the highlighted part) with your own email address:
email nagios@localhost ; <<***** CHANGE THIS TO YOUR
EMAIL ADDRESS ******
Save and exit.
Configure
check_nrpe Command
Let's add a new command to our
Nagios configuration:
·
sudo vi
/usr/local/nagios/etc/objects/commands.cfg
·
Add the following to the end of the
file:
define
command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H
$HOSTADDRESS$ -c $ARG1$
}
Save and exit. This allows you to
use the check_nrpe command in your Nagios service definitions.
Configure
Apache
Use htpasswd to create an admin
user, called "nagiosadmin", that can access the Nagios web interface:
sudo
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
Enter a password at the prompt.
Remember this login, as you will need it to access the Nagios web interface.
Note: If you create a user that is not named
"nagiosadmin", you will need to edit /usr/local/nagios/etc/cgi.cfg and change all the "nagiosadmin" references to
the user you created.
Nagios is ready to be started. Let's
do that, and restart Apache:
sudo
systemctl start nagios.service
sudo
systemctl restart httpd.service
To enable Nagios to start on server
boot, run this command:
sudo
chkconfig nagios on
Optional:
Restrict Access by IP Address
If you want to restrict the IP
addresses that can access the Nagios web interface, you will want to edit the
Apache configuration file:
sudo
vi /etc/httpd/conf.d/nagios.conf
Find and comment the following two
lines by adding #
symbols in front of them:
Order
allow,deny
Allow
from all
Then uncomment the following lines,
by deleting the #
symbols, and add the IP addresses or ranges (space delimited) that you want to
allow to in the Allow from line:
# Order deny,allow
# Deny from all
# Allow from 127.0.0.1
As these lines will appear twice in
the configuration file, so you will need to perform these steps once more.
Save and exit.
Now start Nagios and restart Apache
to put the change into effect:
sudo
systemctl restart nagios.service
sudo
systemctl restart httpd.service
Nagios is now running, so let's try
and log in.
Accessing
the Nagios Web Interface
Open your favorite web browser, and
go to your Nagios server (substitute the IP address or hostname for the
highlighted part):
http://nagios_server_public_ip/nagios
Because we configured Apache to use
htpasswd, you must enter the login credentials that you created earlier. We
used "nagiosadmin" as the username:
After authenticating, you will be see
the default Nagios home page. Click on the Hosts link, in the left
navigation bar, to see which hosts Nagios is monitoring:
As you can see, Nagios is monitoring
only "localhost", or itself.
Let's monitor another host with
Nagios!
Monitor
a CentOS 7 Host with NRPE
In this section, we'll show you how
to add a new host to Nagios, so it will be monitored. Repeat this section for
each CentOS or RHEL server you wish to monitor.
Note: If you want to monitor an Ubuntu or Debian server, follow
the instructions in this link: Monitor an Ubuntu Host with NRPE.
On a server that you want to
monitor, install the EPEL repository:
sudo
yum install epel-release
Now install Nagios Plugins and NRPE:
sudo
yum install nrpe nagios-plugins-all
Now, let's update the NRPE
configuration file. Open it in your favorite editor (we're using vi):
sudo
vi /etc/nagios/nrpe.cfg
Find the allowed_hosts directive, and add the private IP address of your Nagios
server to the comma-delimited list (substitute it in place of the highlighted
example):
allowed_hosts=127.0.0.1,10.132.224.168
Save and exit. This configures NRPE
to accept requests from your Nagios server, via its private IP address.
Restart NRPE to put the change into
effect:
sudo
systemctl start nrpe.service
sudo
systemctl enable nrpe.service
Once you are done installing and
configuring NRPE on the hosts that you want to monitor, you will have to add
these hosts to your Nagios server configuration before it will start monitoring
them.
Add
Host to Nagios Configuration
On your Nagios server, create a new
configuration file for each of the remote hosts that you want to monitor in /usr/local/nagios/etc/servers/. Replace the highlighted word, "yourhost", with
the name of your host:
sudo
vi /usr/local/nagios/etc/servers/yourhost.cfg
Add in the following host
definition, replacing the host_name value with your remote hostname ("web-1" in the
example), the alias
value with a description of the host, and the address value with the private IP address of the remote host:
define
host {
use linux-server
host_name yourhost
alias My first Apache
server
address 10.132.234.52
max_check_attempts 5
check_period 24x7
notification_interval 30
notification_period 24x7
}
With the configuration file above,
Nagios will only monitor if the host is up or down. If this is sufficient for
you, save and exit then restart Nagios. If you want to monitor particular
services, read on.
Add any of these service blocks for
services you want to monitor. Note that the value of check_command determines
what will be monitored, including status threshold values. Here are some
examples that you can add to your host's configuration file:
Ping:
define
service {
use generic-service
host_name yourhost
service_description PING
check_command
check_ping!100.0,20%!500.0,60%
}
SSH (notifications_enabled set to 0
disables notifications for a service):
define
service {
use generic-service
host_name yourhost
service_description SSH
check_command check_ssh
notifications_enabled 0
}
If you're not sure what use
generic-service means, it is simply inheriting the
values of a service template called "generic-service" that is defined
by default.
Now save and quit. Reload your
Nagios configuration to put any changes into effect:
