Challenge, Medium,  on  Containers

Make a Container Restart Automatically After Docker Host Reboot

In this challenge, you'll make a containerized web application resilient to Docker host reboots.

A web server is already running as a background container named app-1 and serves HTTP traffic on port 8080. You can verify it's working:

curl http://localhost:8080/

Your task is to configure the system and the app-1 container so that it automatically restarts whenever the Docker daemon restarts or the machine reboots.

systemd restarts the Docker daemon, which in turn restarts the container.

First, you need to ensure that the Docker systemd service is enabled:

Hint: Enabling the Docker systemd service

The fact that the docker.service is currently running does not guarantee that it's enabled (i.e. will start automatically on boot). Depending on the server's Linux distribution and configuration, the default Docker installation procedure may or may not enable the service by default, so it's always a good idea to ensure it's enabled.

Next, you need to configure the app-1 container's restart policy to make it resilient to restarts:

Hint: Setting container restart policies

Check out this challenge for a refresher on setting container restart policies:

Docker 101: Restart Containers on Failure Automatically

Once the Docker service is enabled in systemd and the container's restart policy is set, reboot the machine:

sudo reboot

Now let's check if the app-1 container survived the reboot and came back online automatically with the same container ID:

How to Author Challenges on iximiuz Labs

Instead of providing a subpar online editing experience, iximiuz Labs offers a helper CLI tool called labctl, allowing you to use your favorite text editor (or a full-featured IDE) to write content from the comfort of your local machine.

Install labctl CLI

curl -sf https://labs.iximiuz.com/cli/install.sh | sh

This will download and install the latest version of the labctl CLI. You only need to do this once per workstation.

Authorize labctl

labctl auth login

This will open a browser window asking you to authorize labctl to access your account. You need to do it after a fresh install of labctl and repeat it whenever the auth session expires.

Pull challenge content

labctl content pull challenge docker-101-container-restart-on-host-reboot

This will create a local copy of the challenge content in a directory named docker-101-container-restart-on-host-reboot. You only need to do this once per challenge.

Stream your changes

labctl content push -fw challenge docker-101-container-restart-on-host-reboot

Run this command in a separate terminal to continuously upload your changes to the server while editing the challenge in your favorite text editor or IDE.

You can also use labctl to create, list, and delete your content. Learn more about the available commands: labctl content --help

Start challenge