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.

Kebutuhan

• 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 username@your_nagios_server_ip

Instalasi aplikasi pendukung,

sudo apt update
sudo apt -y install autoconf gcc libc6 make wget unzip apache2 php libapache2-mod-php 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/
wget -O nagioscore.tar.gz https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.6.tar.gz
tar xzf nagioscore.tar.gz
cd /usr/local/src/nagioscore-nagios-4.4.6/

Run script & specify Apache config directory:

sudo su
cd /usr/local/src/nagioscore-nagios-4.4.6/
sudo ./configure --with-httpd-conf=/etc/apache2/sites-enabled

Catatan: jika kita menggunakan email server postfix, ada baiknya di tambah --with-mail=/usr/sbin/sendmail

Compile & install Nagios,

cd /usr/local/src/nagioscore-nagios-4.4.6/
sudo make all
sudo make install-groups-users
sudo make install
sudo make install-daemoninit
sudo make install-commandmode
sudo make install-config

Konfigurasi apache

sudo make install-webconf
sudo a2enmod rewrite
sudo a2enmod cgi
sudo usermod -a -G nagios www-data

Konfigurasi & masukan _PASSWORD_ untuk user nagiosadmin (untuk user lain, nagiosadmin bisa di ganti)

sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Catatan: edit /usr/local/nagios/etc/cgi.cfg ubah nagiosadmin ke useranda jika tidak menggunakan nagiosadmin.

Restart Apache,

sudo systemctl restart apache2

Step 2 — Installing 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,

sudo su
cd /usr/local/src
curl -L -O https://nagios-plugins.org/download/nagios-plugins-2.3.3.tar.gz
tar zxf nagios-plugins-2.3.3.tar.gz
cd /usr/local/src/nagios-plugins-2.3.3

Konfigurasi & instalasi:

cd /usr/local/src/nagios-plugins-2.3.3
./configure
sudo make
sudo make install

Step 3 — Installing the check_nrpe Plugin

Nagios me-monitor remote host menggunakan Nagios Remote Plugin Executor (NRPE). NRPE terdiri dari dua bagian,

• check_nrpe plugin (di admin console) yang digunakan di Nagios server.
• NRPE daemon, di remote host dan mengirimkan data ke Nagios server.

Optional untuk mencari kesiapan libssl-dev

apt -y install apt-file
apt-file update
apt-file search libssl | grep libssl-dev
apt-file search libssl | grep /usr/lib/x86_64-linux-gnu
apt-file search ssl | grep /usr/bin/openssl

Install libssl-dev

apt -y install  libssl-dev

Download,

sudo su
cd /usr/local/src
curl -L -O https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-4.0.3/nrpe-4.0.3.tar.gz
tar zxf nrpe-4.0.3.tar.gz
cd /usr/local/src/nrpe-4.0.3

Konfigurasi dan install check_nrpe plugin:

sudo su
cd /usr/local/src/nrpe-4.0.3
./configure --with-ssl=/usr/bin/openssl --with-ssl-lib=/usr/lib/x86_64-linux-gnu
sudo make check_nrpe
sudo make install-plugin

Step 4 — Konfigurasi Nagios server

Konfigurasi awal Nagios, meliputi proses editing beberapa file konfigurasi. Kita hanya perlu melakukannya satu kali di Nagios server.

Edit nagios.cfg

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

Temukan di /usr/local/nagios/etc/nagios.cfg

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

Buang # di depan cfg_dir, menjadi

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

Buat directory tersebut. Ini akan menyimpan file konfigurasi untuk setiap server yang kita monitor,

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

Edit contact

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

Ubah email dengan email kita di /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 ******
...

Edit commands.cfg'

Untuk menambahkan new command ke konfigurasi Nagios.

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

Tambahkan di /usr/local/nagios/etc/objects/commands.cfg

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

Restart Nagios

sudo systemctl start nagios

Step 5 — Akses Nagios Web

Akses ke

http://nagios_server_public_ip/nagios.

username nagiosadmin
password yangkitasetsebelumnya

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 Plugin & NRPE Daemon di Server yang di monitor

Untuk memonitor sebuah server, kita perlu menginstalasi Nagios Remote Plugin Executor (NRPE) di remote host tersebit, install plugin, dan konfigurasi Nagios server.

Login server yang akan di monitor,

ssh onno@your_monitored_server_ip

Buat user nagios yang akan menjalankan NRPE agent,

sudo useradd nagios

Install aplikasi pendukung,

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-2.3.3.tar.gz
tar zxf nagios-plugins-2.3.3.tar.gz
cd nagios-plugins-2.3.4

Compile & install

./configure
make
sudo make install

Install NRPE daemon,

cd /usr/local/src
curl -L -O https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-4.0.3/nrpe-4.0.3.tar.gz
tar zxf nrpe-4.0.3.tar.gz
cd nrpe-4.0.3

Configure & Install NRPE:

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

Untuk ujicoba kita akan monitor penggunan harddisk. Contoh,

df -h /

Akan keluar,

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

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

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

Kita perlu menembukan dan mengubah,

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
...

Start NRPE,

sudo systemctl start nrpe.service

Pastikan running,

sudo systemctl status nrpe.service

output kira2,

...
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

Buka port 5666 di firewall,

sudo ufw allow 5666/tcp

Cek komunikasi ke remote NRPE server dari Admin Console (Nagios Server),

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

Output,

NRPE v4.0.3

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