DOCKER Interview Questions and Answers- Part 5

Answer:

A self-hosted namespace image usually contains an IP address or the hostname, and the port of the registry server.

Answer:

There are three types of virtualization, such as:

• Paravirtualization
• Emulation
• Container-based virtualization.

Answer:

To achieve multi-host networking in Docker, you can use Docker’s built-in networking features along with external tools or orchestrators. Multi-host networking allows containers to communicate across different Docker hosts or nodes. One common approach is to use Docker’s Swarm mode or Kubernetes for container orchestration.

Answer:

The following drivers are available in pre R1.9 Release of docker Engine

• none
• host
• bridge (default)
• container

Answer:

In Docker, a “null network driver” refers to a network driver that essentially disables network communication for containers. When you run a Docker container, it is assigned a network interface that allows it to communicate with other containers or external resources, such as the internet. However, using the null network driver prevents the container from having any network connectivity.

Answer:

Docker will first remove the stopped containers that are not part of a running or paused service, then Docker will remove the unused volumes without containers. Finally, it deletes the images with no containers.

Answer:

Docker volumes are a crucial feature in the Docker containerization platform that serve as a way to manage and persist data generated or used by Docker containers. The main use of Docker volumes is to ensure the separation of data from the lifecycle of containers, thus enabling data to be shared and preserved even when containers are created, stopped, or removed.

Answer:

You can attain this by utilizing the “docker exec” instruction. By using this command, you have the ability to initiate a fresh procedure within a container that’s currently active. This command allows you to obtain a bash shell interface within a pre-existing container, facilitating real-time debugging.

Answer:

Yes, volumes in Docker can exist independently of containers. Docker volumes are a way to persist and manage data that needs to be shared or preserved between containers. Volumes are separate entities from containers and can exist even when the container that created them is no longer running. This means you can create a volume, attach it to one or more containers, and the data within the volume will persist across container restarts and even if the containers are removed.

Answer:

$docker system prune [OPTIONS] is used to delete all dangling data in Docker.

Answer:

Docker is often considered one of the best container platforms due to several reasons:

• Ease of Use: Docker provides a user-friendly interface and command-line tools that make it simple to create, manage, and deploy containers. This has lowered the barrier for entry, making containerization more accessible.
• Portability: Docker containers encapsulate applications and their dependencies, allowing them to run consistently across different environments, from development to production. This portability helps in avoiding “it works on my machine” issues.
• Isolation: Containers provide a high level of isolation between applications and their dependencies. This isolation ensures that changes to one container do not affect others, improving security and stability.
• Resource Efficiency: Docker containers share the host operating system’s kernel, which makes them lightweight and efficient in terms of resource utilization. This enables running more containers on the same hardware compared to traditional virtual machines.
• Version Control: Docker images can be versioned, allowing you to track changes and roll back if needed. This is beneficial for software development, testing, and deployment processes.
• Scalability: Docker’s architecture makes it easy to scale applications by replicating containers across multiple hosts. This flexibility is crucial for handling varying workloads.
• Ecosystem and Community: Docker has a large and active community that contributes to its ecosystem. This means there are numerous pre-built images available on Docker Hub, which can save time in setting up software stacks.
• Orchestration: Docker provides tools like Docker Swarm and Kubernetes for orchestrating and managing clusters of containers. These tools help automate deployment, scaling, and management of containerized applications.
• Continuous Integration and Deployment (CI/CD): Docker’s containerization is well-suited for CI/CD pipelines. Developers can build and test applications in containers during development and then deploy the exact same containers in production, reducing discrepancies.
• Support for Microservices Architecture: Docker’s containerization aligns well with the microservices architecture, where applications are broken down into smaller, loosely coupled services. Each service can be containerized, making development and maintenance more manageable.

Answer:

You can search and manipulate the information from ‘docker inspect’ using commands like grep, cut, or awk, but this involves using complicated scripting in the command line. A more user-friendly approach is to extract information from the output using a tool called JQ, which can understand JSON data from the Shell.

Answer:

Some of the key security features in Docker include:

1. Isolation: Containers are isolated from each other and from the host system, which helps prevent unauthorized access to resources.
2. Namespaces: Docker uses namespaces to create separate instances of various operating system resources, such as network, process, and file system namespaces. This helps in isolating containers from each other and from the host.
3. Control Groups (cgroups): Docker utilizes cgroups to manage and limit the resources available to containers, preventing resource abuse and ensuring fair allocation of resources.
4. AppArmor and SELinux: These are security profiles that can be applied to containers to restrict their access to host system resources. They help enforce the principle of least privilege.
5. Read-Only File Systems: Docker containers can be configured to run with read-only file systems, reducing the risk of unauthorized changes to critical files.
6. Docker Content Trust: This feature ensures the integrity and authenticity of Docker images by using digital signatures. It prevents the use of tampered or unverified images.
7. User Namespaces: Docker supports user namespaces, which allows container processes to run as non-root users inside the container while mapping them to different user IDs on the host. This enhances security by minimizing the potential impact of container compromise.
8. Image Scanning: Docker Hub and some other container registries offer image scanning tools that check for known vulnerabilities and issues in the images before they are deployed.
9. Secrets Management: Docker provides a way to manage sensitive information such as passwords and API keys as secrets, ensuring they are stored securely and made available to containers only when needed.
10. Network Segmentation: Docker allows you to define custom networks for containers, which enables you to isolate containers and control their communication.

Answer:

You can use –entrypoint to override the ENTRYPOINT at runtime.

Answer:

Tags should be avoided in the following situations:

• During rapid testing and the swift development of application prototypes
• During experimental phases aimed at feature testing
• When you want the most recent version of an image.

Answer:

Docker is focused on containerization and application deployment, ensuring consistency across different environments. Chef, on the other hand, is a configuration management tool that automates server configuration and ensures infrastructure consistency. They can be used together, with Chef helping to manage the configuration of servers on which Docker containers are deployed.

Answer:

You can make a new image by using two commands: “commit” and “build.” When you “commit,” you’re telling the Docker daemon to remember all the changes you’ve made to a container and use those to make a new layer. When you “build,” you’re telling the Docker computer to put together each layer one by one to create a brand new image.

Answer:

Container Networking Model (CNM) is a networking framework used in container orchestration platforms like Docker. It defines a set of rules and conventions for connecting containers within a network. CNM enables containers to communicate with each other and with external systems while abstracting the underlying network infrastructure.

Answer:

We need to map ports in Docker for several reasons, such as:

• Containers cannot have public IPv4 addresses
• We don’t have IPv4 addresses.
• They have private addresses
• Services need to be exposed port by port
• Ports should be mapped to avoid conflicts

Answer:

A stateless application proves to be better suited for Docker containers than a stateful application. The advantage lies in the clear separation between the application’s code (encapsulated as an image) and its configurable variables within a stateless setup. This arrangement allows the creation of distinct containers for development, integration, and production purposes. As a result, it fosters both reusability and scalability.