Nagios Core

Prerequisites

Before you launch this AMI, make sure you have:

• An active AWS account
• An active subscription to the Nagios Core listing on AWS Marketplace
• An EC2 key pair for SSH access
• Familiarity with EC2 instance management and SSH

Recommended instance type: t3.small (2 vCPU, 2 GB RAM) or larger. The minimum requirements are 1 vCPU, 1 GB RAM and 20 GB of disk space.

Adding a Host to Monitor

To add a host to monitor, create a configuration file:

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

Example host configuration:

define host { use linux-server host_name web-server-01 alias Production Web Server address 10.0.1.100 max_check_attempts 5 check_period 24x7 notification_interval 30 notification_period 24x7 } define service { use generic-service host_name web-server-01 service_description PING check_command check_ping!100.0,20%!500.0,60% } define service { use generic-service host_name web-server-01 service_description SSH check_command check_ssh }

Include the new configuration file in the main Nagios config:

echo "cfg_file=/usr/local/nagios/etc/objects/myserver.cfg" >> /usr/local/nagios/etc/nagios.cfg

Verify the configuration:

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Restart Nagios to apply the changes:

systemctl restart nagios

Server Components

Component Install Path

Nagios Core /usr/local/nagios

Note: the automatic OS package update script may update component versions on first boot.

Filesystem Layout

Mount Point Size Description

/ 38 GB Root filesystem

/boot 2 GB Operating system kernel files

Key Nagios directories:

Directory Purpose

/usr/local/nagios Nagios installation root

/usr/local/nagios/etc Configuration files

/usr/local/nagios/etc/objects Host, service, and command definitions

/usr/local/nagios/bin Nagios binaries

/usr/local/nagios/libexec Check plugins

/usr/local/nagios/var Runtime data and logs

/usr/local/nagios/share Web interface files

Managing Services

Nagios:

systemctl status nagios
systemctl stop nagios
systemctl start nagios
systemctl restart nagios

Apache HTTP Server:

systemctl status httpd
systemctl stop httpd
systemctl start httpd

Scripts and Log Files

Script/Log Path Description

initial_boot_update.sh /stage/scripts Updates the OS with the latest packages on first boot

initial_boot_update.log /stage/scripts Output log for the boot update script

mysql_root_password.log /stage/scripts MySQL root database password

nagios-credentials.log /stage/scripts Nagios administrator credentials

On Startup

An OS package update script runs on first boot to bring the image fully up to date. To disable it, remove the script and its crontab entry:

rm -f /stage/scripts/initial_boot_update.sh crontab -e
# Delete the following line, save and exit: @reboot /stage/scripts/initial_boot_update.sh

Troubleshooting

Cannot access Nagios on port 80

• Verify that Apache is running: systemctl status httpd
• Verify that Nagios is running: systemctl status nagios
• Check that your security group allows port 80 from your IP.
• Check the Apache error logs: tail -f /var/log/httpd/error_log

Nagios configuration error after adding hosts

• Always verify before restarting: /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
• Check the configuration file for syntax errors.
• Make sure all referenced commands and templates exist.

Notifications not being sent

• Check that notification commands are configured in /usr/local/nagios/etc/objects/commands.cfg.
• Verify the contact email addresses in /usr/local/nagios/etc/objects/contacts.cfg.
• Make sure the mail service is configured on the instance.

Cannot log in to Nagios web interface

• Verify the credentials from /stage/scripts/nagios-credentials.log.
• Reset the nagiosadmin password: htpasswd /usr/local/nagios/etc/htpasswd.users nagiosadmin

Security Recommendations

• Change the nagiosadmin password after your first login, using htpasswd.
• Restrict port access. Allow port 80 from trusted IPs only.
• Enable HTTPS. Configure Apache with SSL for encrypted access to the monitoring console.
• Secure the credential files. Delete /stage/scripts/nagios-credentials.log after you record the values.
• Use NRPE for remote checks. Install the NRPE agent on monitored hosts for secure local checks.
• Limit command execution. Restrict which external commands can be run through the web interface.
• Keep Nagios updated. Apply security patches when they are available.
• Monitor the monitor. Set up external health checks for the Nagios instance itself.

Support

If you have any issues with this product, contact SecureAnyCloud support:

• Email: sales@secureanycloud.com
• Website: secureanycloud.com
• Support hours: 24/7, with a 24 hour response SLA

Deploy on AWS

Launch Nagios Core with 24/7 support from SecureAnyCloud.

View on Marketplace

Need Help?

Our support team is available 24/7.

sales@secureanycloud.com

Prerequisites

You need an active Azure subscription, an SSH key pair, and a VNet with a subnet in the target region.

Standard_B2s is a good starting size. Choose a larger size to monitor many hosts.

Configure the network security group (NSG) to allow inbound 22/tcp from your management network and 80/tcp from the networks that need the Nagios UI. For public exposure, front port 80 with TLS (see Enabling HTTPS).

Step 1 - Deploy from the Azure Marketplace

Sign in to the Azure Portal, choose Create a resource, search the Marketplace for Nagios Core by SecureAnyCloud, and select Create.

On the Basics tab, pick your subscription, resource group, region and size. Under Administrator account, choose SSH public key and paste your key. Under Inbound port rules, allow SSH (22) and HTTP (80).

Then select Review + create and Create.

Step 2 - Deploy from the Azure CLI

# Accept the Marketplace terms once per subscription (required before the first CLI deploy)
az vm image terms accept --urn sac1647283583153:nagios-core-ubuntu-24-04:default:latest
az vm create \
  --resource-group <your-rg> \
  --name nagios \
  --image sac1647283583153:nagios-core-ubuntu-24-04:default:latest \
  --size Standard_B2s \
  --admin-username azureuser \
  --ssh-key-values ~/.ssh/id_ed25519.pub \
  --vnet-name <your-vnet> --subnet <your-subnet> \
  --public-ip-sku Standard
az vm open-port --resource-group <your-rg> --name nagios --port 80 --priority 1010

Step 3 - Connect to your VM

ssh azureuser@<vm-public-ip>

Step 4 - Confirm the services are running

systemctl is-active nagios4.service apache2.service curl -s -o /dev/null -w '%{http_code}\n' http://127.0.0.1/health.txt

Both services report active. The unauthenticated health endpoint returns 200.

Step 5 - Retrieve your admin password

The first boot of your VM generates a unique password and writes it to a root-only file:

sudo cat /root/nagios-credentials.txt

The username is nagiosadmin. The password is the NAGIOS_ADMIN_PASSWORD value.

Step 6 - Sign in to the web UI

Browse to http://<vm-public-ip>/nagios4/ and sign in with nagiosadmin and the password from Step 5.

You can also confirm the authenticated endpoint from the shell. Without credentials it returns 401, and with them it returns 200:

PW=$(sudo grep '^NAGIOS_ADMIN_PASSWORD=' /root/nagios-credentials.txt | cut -d= -f2-)
echo "unauthenticated: $(curl -s -o /dev/null -w '%{http_code}' http://127.0.0.1/nagios4/)"
echo "authenticated: $(curl -s -o /dev/null -w '%{http_code}' -u "nagiosadmin:$PW" http://127.0.0.1/nagios4/)"

Step 7 - Add hosts and services

Nagios object definitions live in /etc/nagios4/. Add host and service definitions under /etc/nagios4/conf.d/ (or the configured cfg_dir), then verify the configuration and reload:

sudo /usr/sbin/nagios4 -v /etc/nagios4/nagios.cfg
sudo systemctl reload nagios4

The config check must report Things look okay before you reload.

Step 8 - Confirm the runtime

/usr/sbin/nagios4 --version | head -2

Enabling HTTPS

For production, terminate TLS at Apache with a real domain pointed at the VM's public IP. Install certbot and request a certificate. Replace the domain with your own:

sudo apt-get update && sudo apt-get install -y certbot python3-certbot-apache
sudo certbot --apache -d your-domain.example.com

Backup and maintenance

Your Nagios configuration lives in /etc/nagios4/. Back up /etc/nagios4/ regularly. Keep the OS patched with sudo apt update && sudo apt upgrade, and validate config changes with nagios4 -v before you reload. The service restarts cleanly with sudo systemctl restart nagios4.

Support

This image is backed by 24/7 SecureAnyCloud support. Contact us by email or chat for help with host and service configuration, notifications, plugins, scaling and TLS.

All product and company names are trademarks or registered trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.

Deploy on Azure

Launch Nagios Core on Ubuntu 24.04 LTS on Azure with 24/7 support from SecureAnyCloud.

View this image

Need Help?

Our support team is available 24/7.

sales@secureanycloud.com