nagios_core_container_experience

nagios_core_container_experience

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# Check if container is running
docker-compose -f docker-compose.yml.ubuntu ps


Check the container is running
docker ps
Look for your Nagios container, something like:
nagios_core   0.0.0.0:8080->80/tcp   Up   nagios:4.5.9

# Check logs for any startup issues
docker-compose -f docker-compose.yml.ubuntu logs nagios459

docker logs <container_name>

Access the web interface

URL:
http://<docker_host_ip>:<mapped_port>


the volume name in your docker-compose.yml.ubuntu is not actually just nagiosetc.
When Docker Compose creates a named volume without an absolute path, it prefixes it with the project name from your compose file.

$ docker volume ls | grep nagiosetc
local     docker-nagios-ubuntu_nagiosetc

How to inspect the right volume
docker volume inspect docker-nagios-ubuntu_nagiosetc

How to avoid the long prefix

If you want your volumes to be exactly nagiosetc, you can:

Run Compose with a custom project name:

docker compose -f docker-compose.yml.ubuntu -p nagios up -d

Or explicitly declare the volume name in your YAML:
volumes:
  nagiosetc:
    name: nagiosetc

Edit configs in the volume
You can either:

Edit directly on the host:
sudo nano /var/lib/docker/volumes/nagiosetc/_data/nagios.cfg

Or enter the container

docker exec -it nagios459 bash
cd /opt/nagios/etc

docker exec -it nagios459 bash ls /opt/nagios/etc

# Enter the running container
docker exec -it nagios459 bash

# Or using docker-compose
docker-compose -f docker-compose.yml.ubuntu exec nagios459 bash

$ docker exec -it nagios459 ls /opt/nagios/etc

docker exec -it nagios459 /usr/local/nagios/libexec/check_nrpe -H 127.0.0.1

Or copy them to your host for easier editing
docker cp nagios459:/opt/nagios/etc ./nagiosetc



Test configuration inside the container
docker exec -it nagios459 /opt/nagios/bin/nagios -v /opt/nagios/etc/nagios.cfg
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Add custom plugins

Put scripts in the customplugins volume:
docker run --rm -it -v customplugins:/data ubuntu bash
# Place your plugin in /data
chmod +x /data/check_myplugin.sh


11. Add Custom Plugins
Your setup has a custom plugins volume. Add plugins to /opt/Custom-Nagios-Plugins/

# Copy plugins from host to container
docker cp ./my-custom-plugin.sh nagios459:/opt/Custom-Nagios-Plugins/

# Make executable
docker exec nagios459 chmod +x /opt/Custom-Nagios-Plugins/my-custom-plugin.sh
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Backup your configs

Since these are Docker named volumes, back them up with:
docker run --rm -v nagiosetc:/data -v $(pwd):/backup ubuntu tar czf /backup/nagiosetc-backup.tar.gz -C /data .
docker run --rm -v nagiosvar:/data -v $(pwd):/backup ubuntu tar czf /backup/nagiosvar-backup.tar.gz -C /data .

# Create backup of configuration volume
docker run --rm -v nagios459_nagiosetc:/data -v $(pwd):/backup alpine tar czf /backup/nagios-config-$(date +%Y%m%d).tar.gz -C /data .
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13. Monitor Container Health

# Check container stats
docker stats nagios459

# Check disk usage of volumes
docker system df -v

14. Configure NagiosGraph (Since It's Included)
Check NagiosGraph configuration:

ls -la /opt/nagiosgraph/etc/
ls -la /opt/nagiosgraph/var/
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5. Initial Configuration Setup
Inside the container, check key directories:

# Main configuration
ls -la /opt/nagios/etc/

# Configuration files
ls -la /opt/nagios/etc/objects/

# Custom plugins location
ls -la /opt/Custom-Nagios-Plugins/

# Runtime data
ls -la /opt/nagios/var/
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Validate Configuration
Always validate before restarting:
/opt/nagios/bin/nagios -v /opt/nagios/etc/nagios.cfg

10. Restart Nagios Service
Inside the container:

# Check if Nagios is running
ps aux | grep nagios

# Restart Nagios
service nagios restart



# Or reload configuration
service nagios reload

# service nagios restart
nagios: unrecognized service

/# systemctl status nagios 2>/dev/null || echo "systemctl not available"
systemctl not available


# Check for init scripts
ls -la /etc/init.d/ | grep nagios

/etc/init.d/nagios restart

Restart Methods (Try These in Order)
Method 1: Direct Process Control

# Kill current Nagios process
pkill nagios

# Start Nagios directly
/opt/nagios/bin/nagios -d /opt/nagios/etc/nagios.cfg


Reload Configuration Without Full Restart
Send HUP signal to reload config:

# Find Nagios PID
cat /opt/nagios/var/nagios.lock

# Send reload signal (replace PID_NUMBER with actual PID)
kill -HUP PID_NUMBER

# Or use pkill
pkill -HUP nagios
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Alternative: Restart from Outside Container
From your host system:

# Restart the entire container
docker-compose -f docker-compose.yml.ubuntu restart nagios459

# Or stop and start
docker-compose -f docker-compose.yml.ubuntu stop nagios459
docker-compose -f docker-compose.yml.ubuntu start nagios459
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Verify Nagios is Running After Restart

# Check process
ps aux | grep nagios

# Check web interface
curl -I http://localhost/nagios/

# Check if it's listening on port 80
netstat -tlnp | grep :80

# Verify configuration was loaded
tail -f /opt/nagios/var/nagios.log
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# 1. Validate config first
/opt/nagios/bin/nagios -v /opt/nagios/etc/nagios.cfg

# 2. If validation passes, restart Nagios directly
pkill nagios
/opt/nagios/bin/nagios -d /opt/nagios/etc/nagios.cfg

# 3. Verify it's running
ps aux | grep nagios

docker-compose -f docker-compose.yml.ubuntu restart nagios459
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Nagios Core does not have true “auto-discovery” like some enterprise monitoring platforms (e.g., Zabbix, PRTG, or LibreNMS).
Nagios Core is configuration-driven, meaning it monitors only the hosts and services you explicitly define.

Important Notes

Nagios Core itself won’t automatically add hosts or services — you always need some script or automation to feed it configs.

Using auto-discovery scripts often requires careful testing — you don’t want hundreds of hosts added accidentally.

For containers, you can mount a directory like nagiosetc/auto and reload Nagios after scripts generate config files there.

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Using NRPE or NCPA for agent auto-registration

Remote hosts run NRPE or NCPA agents.

You can write a small script that detects newly installed agents and appends host/service definitions automatically to Nagios configs.
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Using configuration management tools

Tools like Ansible, Puppet, or Chef can:

Scan your network or inventory

Automatically generate Nagios config files

Deploy them to the Nagios server (or container)

Reload Nagios
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This is the closest to “auto-discovery” for Nagios Core

Third-party scripts/plugins

There are community scripts like nagios-discover or nagios-autodiscover that combine network scanning + config generation.

Typically, they:

Scan a network

Detect OS/services

Generate host/service definitions

Reload Nagios
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Using Nmap or network scanning scripts

You can scan a subnet to find hosts, then automatically generate Nagios host definitions.

nmap -sn 192.168.1.0/24 -oG - | awk '/Up$/{print $2}' > hosts.txt

Then generate define host{} blocks from hosts.txt:

awk '{print "define host{\n use linux-server\n host_name host"$1"\n address "$1"\n}\n"}' hosts.txt > newhosts.cfg


Place newhosts.cfg in /usr/local/nagios/etc/objects/ (or your container’s nagiosetc volume) and reference it in nagios.cfg.

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