Docker Nagios

Docker image for Nagios, the Industry Standard in IT Infrastructure Monitoring. Nagios Core is running on Alpine Linux, using Apache HTTP as a web server and sSMTP as mail agent for email notifications.

The image is inspired by JasonRivers/Docker-Nagios image (Kudos to Jason!) but follows a different approach targetted to lightweight size and basic features.

Build Status:

• Available architectures: x86, amd64, arm/v6, arm/v7, arm64
• Where to file issues: https://github.com/manios/docker-nagios/issues

Supported tags and respective Dockerfile links

• 4.5.10, 4.5, latest (4.5.10/Dockerfile)

For more information about the image versions you may refer to the CHANGELOG

Container registries

Since build-23 (CHANGELOG), the Nagios Docker image is available in Dockerhub and Github Container Registry (GHCR). You can pull it using one of the following ways:

1. Dockerhub: docker pull manios/nagios:latest
2. Github Container Registry: docker pull ghcr.io/manios/nagios:latest

Running

Run with the example configuration with the following:

docker run --name nagios -p 0.0.0.0:8080:80 manios/nagios:latest

alternatively you can use external Nagios configuration & log data with the following:

docker run --name nagios  \
  -v /path-to-nagios/etc/:/opt/nagios/etc/ \
  -v /path-to-nagios/var:/opt/nagios/var/ \
  -v /path-to-nagios/ssmtp.conf:/etc/ssmtp/ssmtp.conf \
  -v /path-to-custom-plugins:/opt/Custom-Nagios-Plugins \
  -p 0.0.0.0:8080:80 \
  manios/nagios:latest

Notes:

1. The container populates with default configuration files if the configuration directories are empty.
2. The path for the custom plugins will be /opt/Custom-Nagios-Plugins, you will need to reference this directory in your configuration scripts.
3. In order to receive mail notifications, you have to configure SSMTP. You can find example configuration inside the container in the file /etc/ssmtp/ssmtp.conf or in the repository in overlay/etc/ssmtp/ssmtp.conf.

For best results your Nagios container should have access to both IPv4 & IPv6 networks.

Credentials

The default credentials for the web interface is nagiosadmin / nagios. However you can define your own credentials by overriding NAGIOSADMIN_USER and NAGIOSADMIN_PASS when you run the container. For example:

docker run --name nagios  \
  -e NAGIOSADMIN_USER="godmode" \
  -e NAGIOSADMIN_PASS="super-Duper-Secret!" \
  -p 0.0.0.0:8080:80 \
  manios/nagios:latest

Timezones

By default the Alpine container and Nagios both use UTC. In order to change the timezone we can pass the tz timezone database name as an environmental variable in docker run such as:

docker run -e "TZ=Europe/Athens" manios/nagios:latest

This will configure and use globally "Europe/Athens" in both container and Nagios process.

Init scripts

Since tag build-31 the docker image is able to run custom init scripts at the first time the container runs. This is useful if you want to install extra software and plugins, customise the container or execute any initialisation script of your choice.

This feature has the following characteristics in detail:

• You can run one or more init scripts which have to be present in the /container-entrypoint-init-scripts container directory.
• The custom init script(s) run to completion at the first container run.
• Nagios process starts after all init scripts complete successfully.
• If any init script throws an error, the container is restarted.
• When all init scripts run to completion (exit code 0), a special file is written to the container filesystem, in the path ${NAGIOS_HOME}/container_first_run. This file acts as a flag which verifies that the init scripts will be executed only on the first run.
• If you want your init scripts to run in a specific order, then make sure to name them by using a numeric prefix such as:
  1. 0001-install-mongodb.sh
  2. 0002-install-jq.sh
  3. 0003-configure-custom-plugins.sh

You can also use a volume mount for your init scripts which can survive container deletions:

docker run -d --name nagios \
    -p 8080:80 \
    -v "$(pwd)/customscripts:/container-entrypoint-init-scripts" \
    manios/nagios:latest

For a detailed example you can have a look here: https://github.com/manios/docker-nagios/issues/96.

Flavours

This Docker image is designed with optimising resources usage in mind and is build for multiple hardware architectures. The following matrix can be used to determine if your hardware architecture is represented in a docker image tag:

Hardware	Image OS/Arch
PC (32bit)	linux/i386
PC (64bit)	linux/amd64
Raspberry Pi 1	linux/arm/v6
Raspberry Pi 2	linux/arm/v7
Raspberry Pi 3	linux/arm/v7 or linux/arm64
Raspberry Pi 4	linux/arm/v7 or linux/arm64
Apple Silicon M1	linux/arm64

Test configuration

To check if your Nagios configuration is OK, you can run the following while your container is running. We assume that you use /opt/nagios/etc/nagios.cfg as your main configuration file.

docker exec -it mynagioscontainer bin/nagios -v etc/nagios.cfg

Custom plugins

This image comes with the official Nagios Plugins preinstalled in order to remain lightweight in size. If you want to use custom plugins, you can install them in the /opt/Custom-Nagios-Plugins by using init scripts.

Troubleshooting

Nagios keeps restarting or shows a strange behaviour

In docker tag build-5, build-6, build-7 we have used Alpine 3.14 as our base image. This comes with security updates which may cause trouble as described in Release Notes forAlpine 3.14.0 > faccessat2.

In order to resolve this issue you should use docker tag build-8 or you can follow the workarounds provided here: #32 (comment).

My image does not run on Raspberry Pi

As already mentioned in #17, sometimes, because docker manifest related features are still experimental (after 2+ years of their introduction) it has happened when we tested in Raspberry Pi 1 (arm-v6) and Raspberry Pi 3 (arm-v7) that it does not download the arm image but the amd64.

Thus you can define explicitly which architecture to pull:

docker pull --platform=linux/arm/v6 manios/nagios
# or
docker pull --platform=linux/arm/v7 manios/nagios

and it works. Be advised that the --platform switch requires that you enable the Docker Experimental Features.