NaGIOS 4: UBUNTU 20.04 instalasi NaGIOS

Sumber: https://www.digitalocean.com/community/tutorials/how-to-install-nagios-4-and-monitor-your-servers-on-ubuntu-18-04

Nagios adalah sistem pemantauan open-source yang populer. Nagios menjaga inventory server anda dan memonitor mereka sehingga anda tahu layanan penting anda sudah up dan running. Menggunakan sistem pemantauan seperti Nagios adalah tool penting untuk lingkungan produksi apa pun, karena dengan memantau waktu kerja, penggunaan CPU, atau disk space, anda dapat mencegah masalah sebelum terjadi, atau sebelum pengguna anda menghubungi anda.

Disini kita akan menginstalasi Nagios 4 dan mengkonfigurasinya agar kita dapat memonitor resource host di interface web Nagios. Kita juga akan mensetup Nagios Remote Plugin Executor (NRPE), yang akan berjalan sebagai agent remote host sehingga kita dapat memonitor resource-nya.

Prerequisit

• Dua Ubuntu 20.04 server dengan user root privige. Firewall dengan ufw.
  • Server dengan Nagios akan di sebut Nagios server.
  • Server tanpa Nagios akan di sebut Ubuntu server.
• Nagios Server akan menjalakan Apache dan PHP.

Nagios Server biasanya di jalankan di belakang Firewall atau VPN. Jika di jalankan di IP Public anda harus lebih serius menginstalasi TLS/SSL dll. Tutorial ini berasumsi, Nagios server di belakang Firewall.

Step 1 — Installing Nagios 4

Login ke Nagios server,

   ssh sammy@your_nagios_server_ip

Instalasi aplikasi pendukung,

sudo apt update
sudo apt -y install autoconf gcc libc6 make wget unzip apache2 php libapache2-mod-php7.2 libgd-dev
# sudo apt -y install autoconf gcc make unzip libgd-dev libmcrypt-dev libssl-dev dc snmp libnet-snmp-perl gettext

Download source code terakhir Nagios (misalnya),

   cd /usr/local/src/
   curl -L -O https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.4.tar.gz
   tar zxf nagios-4.4.4.tar.gz
   cd nagioscore-nagios-4.4.4

Before building Nagios, run the configure script and specify the Apache configs directory:

   ./configure --with-httpd-conf=/etc/apache2/sites-enabled

Note: If you want Nagios to send emails using Postfix, you must install Postfix and configure Nagios to use it by adding --with-mail=/usr/sbin/sendmail to the configure command. We won’t cover Postfix in this tutorial, but if you choose to use Postfix and Nagios later, you’ll need to reconfigure and reinstall Nagios to use Postfix support.

You’ll see the following output from the configure command:

Output

• • • Configuration summary for nagios 4.4.4 2019-07-29 ***:

General Options:
-------------------------
       Nagios executable:  nagios
       Nagios user/group:  nagios,nagios
      Command user/group:  nagios,nagios
            Event Broker:  yes
       Install ${prefix}:  /usr/local/nagios
   Install ${includedir}:  /usr/local/nagios/include/nagios
               Lock file:  /run/nagios.lock
  Check result directory:  /usr/local/nagios/var/spool/checkresults
          Init directory:  /lib/systemd/system
 Apache conf.d directory:  /etc/apache2/sites-enabled
            Mail program:  /bin/mail
                 Host OS:  linux-gnu
         IOBroker Method:  epoll

Web Interface Options:
------------------------
                HTML URL:  http://localhost/nagios/
                 CGI URL:  http://localhost/nagios/cgi-bin/
Traceroute (used by WAP):

Review the options above for accuracy. If they look okay, type 'make all' to compile the main program and CGIs.

Now compile Nagios with this command:

make all

Next create a nagios user and nagios group. They will be used to run the Nagios process:

sudo make install-groups-users

Now run these make commands to install Nagios binary files, service files, and its sample configuration files:

sudo make install
sudo make install-daemoninit
sudo make install-commandmode
sudo make install-config

You’ll use Apache to serve Nagios’ web interface, so run the following to install the Apache configuration files and configure its settings:

sudo make install-webconf

Enable the Apache rewrite and cgi modules with the a2enmod command:

sudo a2enmod rewrite
sudo a2enmod cgi

In order to issue external commands via the web interface to Nagios, add the web server user, www-data, to the nagios group:

sudo usermod -a -G nagios www-data

Use the htpasswd command 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 password, as you will need it to access the Nagios web interface.

Warning: If you create a user with a name other than nagiosadmin, you will need to edit /usr/local/nagios/etc/cgi.cfg and change all the nagiosadmin references to the user you created.

Restart Apache to load the new Apache configuration:

sudo systemctl restart apache2

You’ve now installed Nagios. But for this to work, it is necessary to install the Nagios Plugins, which you’ll cover in the next step.

Step 2 — Installing the Nagios Plugins

Kita perlu menginstalasi Nagios plugin, ada sekitar 50 plugin untuk memonitor berbagai hal seperti uptime, disk usage, swap usage, NTP dll. Download plugin,

cd /usr/local/src
curl -L -O https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
tar zxf nagios-plugins-2.2.1.tar.gz
cd nagios-plugins-2.2.1

Next configure their installation:

./configure
make
sudo make install

Now the plugins are installed, but you need one more plugin for monitoring remote servers. Let’s install it next.

Step 3 — Installing the check_nrpe Plugin

Nagios monitors remote hosts using the Nagios Remote Plugin Executor, or NRPE. It consists of two pieces:

• The check_nrpe plugin that the Nagios server uses.
• The NRPE daemon, which runs on the remote hosts and sends data to the Nagios server.

Download,

cd /usr/local/src
curl -L -O https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-3.2.1/nrpe-3.2.1.tar.gz
tar zxf nrpe-3.2.1.tar.gz
cd nrpe-3.2.1

Configure the check_nrpe plugin:

./configure
make check_nrpe
sudo make install-plugin

Let’s configure the Nagios server next.

Step 4 — Configuring Nagios

Now let’s perform the initial Nagios configuration, which involves editing some configuration files. You only need to perform this section once on your Nagios server.

Open the main Nagios configuration file in your preferred text editor. Here, you’ll use nano:

   sudo nano /usr/local/nagios/etc/nagios.cfg

Find this line in the file:

/usr/local/nagios/etc/nagios.cfg

...
#cfg_dir=/usr/local/nagios/etc/servers
...

Uncomment this line by deleting the # character from the front of the line:

/usr/local/nagios/etc/nagios.cfg

cfg_dir=/usr/local/nagios/etc/servers

Save and close nagios.cfg by pressing CTRL+X, followed by Y, and then ENTER (if you’re using nano).

Now create the directory that will store the configuration file for each server that you will monitor:

sudo mkdir /usr/local/nagios/etc/servers

Open the Nagios contacts configuration in your text editor:

sudo nano /usr/local/nagios/etc/objects/contacts.cfg

Find the email directive and replace its value with your own email address:

/usr/local/nagios/etc/objects/contacts.cfg

...
define contact{
        contact_name  nagiosadmin     ; Short name of user
        use           generic-contact ; Inherit default values from generic-contact template (defined above)
        alias         Nagios Admin    ; Full name of user
        email         your_email@your_domain.com  ; <<***** CHANGE THIS TO YOUR EMAIL ADDRESS ******
...

Save and exit the editor.

Next, add a new command to your Nagios configuration that lets you use the check_nrpe command in Nagios service definitions. Open the file /usr/local/nagios/etc/objects/commands.cfg in your editor:

sudo nano /usr/local/nagios/etc/objects/commands.cfg

Add the following to the end of the file to define a new command called check_nrpe: /usr/local/nagios/etc/objects/commands.cfg

...
define command{
        command_name check_nrpe
        command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}

This defines the name and specifies the command-line options to execute the plugin.

Save and exit the editor.

Then start Nagios and enable it to start when the server boots:

sudo systemctl start nagios

Nagios is now running, so let’s log in to its web interface.

Step 5 — Accessing the Nagios Web Interface

Open your favorite web browser, and go to your Nagios server by visiting http://nagios_server_public_ip/nagios.

Enter the login credentials for the web interface in the popup that appears. Use nagiosadmin for the username, and the password you created for that user.

After authenticating, you will see the default Nagios home page. Click on the Hosts link in the left navigation bar to see which hosts Nagios is monitoring:

Nagios Hosts Page

As you can see, Nagios is monitoring only “localhost”, or itself.

Let’s monitor our other server with Nagios,

Step 6 — Installing Nagios Plugins and NRPE Daemon on a Host

Let’s add a new host so Nagios can monitor it. You’ll install the Nagios Remote Plugin Executor (NRPE) on the remote host, install some plugins, and then configure the Nagios server to monitor this host.

Log in to the second server, which we’ll call the second Ubuntu server:

ssh sammy@your_monitored_server_ip

First create a nagios user which will run the NRPE agent:

sudo useradd nagios

You’ll install NRPE from source, which means you’ll need the same development libraries you installed on the Nagios server in Step 1. Update your package sources and install the NRPE prerequisites:

sudo apt update
sudo apt install autoconf gcc libmcrypt-dev make libssl-dev wget dc build-essential gettext

NRPE requires that Nagios Plugins is installed on the remote host. Let’s install this package from source.

Find the latest release of Nagios Plugins from the downloads page.

Download Nagios Plugins to your home directory with curl:

cd /usr/local/src
curl -L -O https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
tar zxf nagios-plugins-2.2.1.tar.gz
cd nagios-plugins-2.2.1

Before building Nagios Plugins, configure them with the following command:

./configure
make
sudo make install

Next, install NRPE daemon. Find the download URL for the latest stable release of NRPE at the GitHub page just like you did in Step 3. Download the latest stable release of NRPE to your monitored server’s home directory with curl:

cd /usr/local/src
curl -L -O https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-3.2.1/nrpe-3.2.1.tar.gz
tar zxf nrpe-3.2.1.tar.gz
cd nrpe-3.2.1

Configure & Install NRPE:

./configure
make nrpe
sudo make install-daemon
sudo make install-config
sudo make install-init

Now, let’s update the NRPE configuration file and add some basic checks that Nagios can monitor.

First, let’s monitor the disk usage of this server. Use the df -h command to look for the root filesystem. You’ll use this filesystem name in the NRPE configuration:

df -h /

You’ll see output similar to this:

Output
Filesystem      Size  Used Avail Use% Mounted on
/dev/vda1        25G  1.4G   23G   6% /

Now open /usr/local/nagios/etc/nrpe.cfg file in your editor:

sudo nano /usr/local/nagios/etc/nrpe.cfg

The NRPE configuration file is very long and full of comments. There are a few lines that you will need to find and modify:

   server_address: Set to the private IP address of the monitored server.
   allowed_hosts: Add the private IP address of your Nagios server to the comma-delimited list.
   command[check_hda1]: Change /dev/hda1 to whatever your root filesystem is called.

Locate these settings and alter them appropriately:

/usr/local/nagios/etc/nrpe.cfg

...
server_address=second_ubuntu_server_private_ip
...
allowed_hosts=127.0.0.1,::1,your_nagios_server_private_ip
...
command[check_vda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/vda1
...

Save and exit the editor. Now you can start NRPE:

sudo systemctl start nrpe.service

Ensure that the service is running by checking its status:

sudo systemctl status nrpe.service

You’ll see the following output:

Output

...
Aug 01 06:28:31 client systemd[1]: Started Nagios Remote Plugin Executor.
Aug 01 06:28:31 client nrpe[8021]: Starting up daemon
Aug 01 06:28:31 client nrpe[8021]: Server listening on 0.0.0.0 port 5666.
Aug 01 06:28:31 client nrpe[8021]: Server listening on :: port 5666.
Aug 01 06:28:31 client nrpe[8021]: Listening for connections on port 5666
Aug 01 06:28:31 client nrpe[8021]: Allowing connections from: 127.0.0.1,::1,165.22.212.38

Next, allow access to port 5666 through the firewall. If you are using UFW, configure it to allow TCP connections to port 5666 with the following command:

sudo ufw allow 5666/tcp

You can learn more about UFW in How To Set Up a Firewall with UFW on Ubuntu 18.04.

Now you can check the communication with the remote NRPE server. Run the following command on the Nagios server:

/usr/local/nagios/libexec/check_nrpe -H second_ubuntu_server_ip

You’ll see the following output:

Output

NRPE v3.2.1

Repeat the steps in this section for each additional server you want to monitor.

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. Let’s do that next.

Step 7 — Monitoring Hosts with Nagios

To monitor your hosts with Nagios, you’ll add configuration files for each host specifying what you want to monitor. You can then view those hosts in the Nagios web interface.

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, monitored_server_host_name with the name of your host:

sudo nano /usr/local/nagios/etc/servers/your_monitored_server_host_name.cfg

Add the following host definition, replacing the host_name value with your remote hostname, the alias value with a description of the host, and the address value with the private IP address of the remote host:

/usr/local/nagios/etc/servers/your_monitored_server_host_name.cfg

define host {
        use                             linux-server
        host_name                       your_monitored_server_host_name
        alias                           My client server
        address                         your_monitored_server_private_ip
        max_check_attempts              5
        check_period                    24x7
        notification_interval           30
        notification_period             24x7
}

With this configuration, Nagios will only tell you if the host is up or down. Let’s add some services to monitor.

First, add this block to monitor load average:

/usr/local/nagios/etc/servers/your_monitored_server_host_name.cfg

define service {
        use                             generic-service
        host_name                       your_monitored_server_host_name
        service_description             Load average
        check_command                   check_nrpe!check_load
}

The use generic-service directive tells Nagios to inherit the values of a service template called generic-service, which is predefined by Nagios.

Next, add this block to monitor disk usage:

/usr/local/nagios/etc/servers/your_monitored_server_host_name.cfg

define service {
        use                             generic-service
        host_name                       your_monitored_server_host_name
        service_description             /dev/vda1 free space
        check_command                   check_nrpe!check_vda1
}

Now save and quit. Restart the Nagios service to put any changes into effect:

sudo systemctl restart nagios

After several minutes, Nagios will check the new hosts and you’ll see them in the Nagios web interface. Click on the Services link in the left navigation bar to see all of your monitored hosts and services.

Nagios Services Page

Conclusion

You’ve installed Nagios on a server and configured it to monitor load average and disk usage of at least one remote machine.

Now that you’re monitoring a host and some of its services, you can start using Nagios to monitor your mission-critical services. You can use Nagios to set up notifications for critical events. For example, you can receive an email when your disk utilization reaches a warning or critical threshold, or a notification when your main website is down. This way you can resolve the situation promptly, or even before a problem occurs.

Referensi

• https://www.digitalocean.com/community/tutorials/how-to-install-nagios-4-and-monitor-your-servers-on-ubuntu-18-04

Pranala Menarik

• NaGIOS