Scenario 1: Installing Docker and Validating Basic Commands

#Question: You’ve just been assigned a new Linux server and need to install Docker. Walk me through how you’d do it and verify the installation.

#Answer:

"Sure! First, I would update the system packages to make sure I have the latest versions. If I’m working on an Amazon Linux 2 instance, I’d run:

sudo yum update -y

sudo yum install -y docker

For Ubuntu, I’d use:

sudo apt update

sudo apt install -y docker.io

Once installed, I’d start the Docker service and enable it to start at boot:

sudo systemctl start docker

sudo systemctl enable docker

To confirm the installation, I’d check the Docker version:

docker --version

And then, I’d run a simple test container to make sure Docker is working correctly:

docker run hello-world

If this command successfully pulls the hello-world image and displays the welcome message, it means Docker is installed and running properly."

Scenario 2: Running a Container, Assigning a Name, and Validating

#Question: Suppose you need to run an Nginx container, assign it a custom name, and check its status. How would you do that?

#Answer:

"I’d use the following command to run an Nginx container and give it a custom name, say `my-nginx`:

docker run -d --name my-nginx -p 8080:80 nginx

Here:

- `-d` runs the container in detached mode, so it runs in the background.

- `--name my-nginx` assigns a custom name instead of a random one.

- `-p 8080:80` maps port 8080 on my host machine to port 80 inside the container, allowing me to access it via `http://localhost:8080`.

To verify that the container is running, I’d use:

docker ps

This would show me a list of running containers, and I should see `my-nginx` in the list.

To confirm it’s serving content, I’d run:

curl http://localhost:8080

If I get an HTML response, that means Nginx is working as expected."

Scenario 3: Exploring Docker Image Search, Naming Conventions, and Setting Up a Docker Hub Repository

#Question: Before using an image, how do you find the official version and ensure it follows best naming practices?

#Answer:

"Great question! First, I’d use the Docker search command to look for an image, ensuring I pull an official one:

docker search nginx

This would return a list of related images. I’d look for the one with the `OFFICIAL` tag in the results to ensure it comes from a trusted source.

Once I find the right image, I’d pull it like this:

docker pull nginx:latest

I always check the naming convention. If it’s an official image, it won’t have a username prefix (e.g., just `nginx` instead of `someuser/nginx`).

If I need to use my own repository, I’d follow the convention `<dockerhub-username>/<project-name>:<tag>`.

For example, before pushing an image, I’d rename it like this:

docker tag nginx:latest mydockerhubuser/nginx-app:v1

And then, I’d set up a repository on Docker Hub and push my image there."

Scenario 4: Pulling an Nginx Image, Tagging It, Logging into Docker Hub, Pushing It, and Verifying

#Question: You need to pull an Nginx image, tag it with your repository name, push it to Docker Hub, and verify it. How would you do that?

#Answer:

"I’d start by pulling the latest Nginx image:

docker pull nginx:latest

Next, I’d tag it with my Docker Hub username and repository:

docker tag nginx:latest mydockerhubuser/nginx-app:v1

Now, before pushing, I’d log in to Docker Hub:

docker login

After entering my credentials, I’d push the tagged image:

docker push mydockerhubuser/nginx-app:v1

To verify, I’d log in to Docker Hub and check if the image is listed under my repository. Alternatively, I could also try pulling it on another machine to make sure it’s publicly accessible or correctly stored."

Scenario 5: Docker Hub Credentials Handling

#Question: Security is a major concern. How would you handle Docker Hub credentials securely instead of storing them in scripts?

#Answer:

"Storing Docker credentials directly in a script is a bad practice. Instead, I follow these secure approaches:

1. Use Interactive Login

Instead of putting credentials in a script, I log in manually when needed:

docker login --username=mydockerhubuser

2. Use CI/CD Secret Storage

If I’m working with Jenkins, GitHub Actions, or AWS CodePipeline, I store my credentials in environment variables or secret managers. For example, in a pipeline:

export DOCKER_USERNAME="mydockerhubuser"

export DOCKER_PASSWORD="mypassword"

echo $DOCKER_PASSWORD | docker login -u $DOCKER_USERNAME --password-stdin

3. Use Docker Credential Store

Docker supports secure credential storage. On Linux, I can configure it to use the `pass` credential helper:

docker-credential-pass list

4. Use a `.docker/config.json` File

If automation requires a config file, I ensure it’s stored securely:

json

{

"auths": {

"https://index.docker.io/v1/": {

"auth": "BASE64_ENCODED_CREDENTIALS"

}

}

}

5. Use AWS Secrets Manager or Vault for Enterprise Solutions

In cloud environments, I’d store credentials securely in AWS Secrets Manager or HashiCorp Vault, retrieving them only when necessary."