Installing Docker and Managing Harness Delegate (Install and Delete) on an Ubuntu Server

In the previous article, OpenSSH was installed on a freshly set-up Ubuntu server inside Proxmox. Now that SSH is working, the server can be used for something useful – hosting a Harness Delegate.

To install a Harness Delegate on a Linux machine, the easiest way is to use Docker.

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Step 1: Check if Docker is Installed

First, check if Docker is already installed by running the command:

docker --version

If the output says that Docker is not found, it needs to be installed. Run the following commands to install Docker:

sudo apt update
sudo apt install -y docker.io

After the installation, enable and start Docker using:

sudo systemctl enable --now docker

Make sure Docker is running by checking its status:

sudo systemctl status docker

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Step 2: Run the Harness Delegate in Docker

Once Docker is running, copy the Docker run command from the Harness dashboard and modify it slightly for better functionality.

Important Notes:

1. Add -d to the docker run command. This will run the container in the background so the delegate logs do not continuously occupy the terminal. If this is not added, the logs will be shown in the terminal, and stopping the logs will stop the container.

2. Always add sudo before the docker run command to avoid permission-related errors.

With these points in mind, the modified command should look like this:

sudo docker run -d --cpus=1 --memory=2g \
-e DELEGATE_NAME=my-test-docker-delegate \
-e NEXT_GEN="true" \
-e DELEGATE_TYPE="DOCKER" \
-e ACCOUNT_ID=predefined_account_id \
-e DELEGATE_TOKEN=predefined_token \
-e DELEGATE_TAGS="" \
-e MANAGER_HOST_AND_PORT=https://app.harness.io/gratis \
harness/delegate:25.02.85300

Once the command is executed, the delegate should show up on the Harness Delegate Dashboard.

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Step 3: Verifying the Delegate Container

To confirm the container is running, use the following command:

sudo docker ps

This will display important details like container ID, image, command, status, and more.

To check the logs of the delegate, use:

sudo docker logs container_id_or_name

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Deleting the Delegate from Docker

If the delegate needs to be removed, follow these steps:

1. Stop the delegate container first with:

sudo docker stop container_id_or_name

2. Once stopped, remove the container:

sudo docker rm container_id_or_name

Optional Commands for Special Cases:

• To force delete a container:

sudo docker rm -f container_id_or_name

• To delete all stopped containers at once:

sudo docker container prune

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Removing Docker Images

If there is a need to remove the images downloaded by the container, follow these steps:

1. List all Docker images:

sudo docker images

2. Remove the intended image by specifying its ID:

sudo docker rmi image_id