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Lab 14

Lab 14: Configuring Nagios on Linux Server and Adding Linux Client

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Option A: Local Setup (VirtualBox)Option B: AWS Setup (EC2 Instances)

1. Prerequisites

• Install VirtualBox (latest version).

• Download:

  • Ubuntu Server ISO (22.04 LTS recommended).
  • Debian/Ubuntu Minimal ISO for client.

2. Create Nagios Server VM

1. Open VirtualBox → New → Name: NagiosServer.

2. Choose:

   • Type: Linux
   • Version: Ubuntu (64-bit)
   • Memory: 2048 MB
   • Disk: 20 GB (VDI, Dynamically allocated)

3. Attach the Ubuntu ISO to the VM and start installation.

4. During install:

   • Set hostname: nagios-server
   • Username: student / Password: student123
   • Install OpenSSH server (select during setup).

3. Install Nagios Core on Server

sudo apt update
sudo apt install -y nagios4 nagios-plugins nagios-nrpe-plugin apache2

• Access web UI:

  • Open browser → http://<server-ip>/nagios4
  • Default user: nagiosadmin (create password with htpasswd).

4. Create Linux Client VM

1. In VirtualBox → New → Name: LinuxClient.
2. Install minimal Ubuntu/Debian with hostname linux-client.
3. Ensure network is Bridged Adapter so both VMs are in same LAN.

5. Install NRPE on Client

sudo apt update
sudo apt install -y nagios-nrpe-server nagios-plugins

• Edit config:

sudo nano /etc/nagios/nrpe.cfg

• Add server IP under:

allowed_hosts=<nagios-server-ip>

• Restart service:

sudo systemctl restart nagios-nrpe-server

6. Add Client to Nagios Server

On Nagios server:

sudo nano /etc/nagios4/conf.d/linuxclient.cfg

Example config:

define host {
    use             linux-server
    host_name       linux-client
    address         <client-ip>
    max_check_attempts  5
    check_period    24x7
    notification_interval 30
    notification_period   24x7
}

• Restart Nagios:

sudo systemctl restart nagios4

✅ Check web UI → you should see linux-client as monitored host.

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1. Setup EC2 Nagios Server

1. Login to AWS Console → EC2 → Launch Instance.
2. Name: NagiosServer.
3. AMI: Ubuntu Server 22.04 LTS (Free Tier).
4. Instance type: t2.micro.
5. Configure Security Group: Allow inbound SSH (22), HTTP (80).
6. Download key pair → nagios-key.pem.
7. Launch instance → Connect via SSH:

chmod 400 nagios-key.pem
ssh -i nagios-key.pem ubuntu@<public-ip>

2. Install Nagios Core

(Same commands as VirtualBox).

3. Setup EC2 Linux Client

1. Launch another EC2 instance: Name LinuxClient.
2. Same AMI and type (t2.micro).
3. Security group: Allow SSH, and allow Nagios server IP on port 5666 (NRPE).
4. Install NRPE (same as VirtualBox client).

4. Add Client to Server

(Same Nagios config steps).

✅ Verify in web UI → client status visible.

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