“Kubernetes vs. Docker” is a phrase that we hear almost everyday as Kubernetes becomes ever more popular as a container orchestration solution. Many of us already know that it is also a misleading phrase because Docker and Kubernetes aren’t competitors. Docker is a containerization platform, and Kubernetes is a container orchestrator for container platforms like Docker.
So, What is Docker?
Docker is a tool designed to make it easier to create, deploy, and run applications by using containers.
Learn more about containers in this post: Containers 101: What Are Containers?
Docker is a set of platform as a service (PaaS) products that uses OS-level virtualization to deliver software in packages called containers. Docker allows applications to use the same Linux kernel as the system that they're running on and only requires applications be shipped with things not already running on the host computer. This gives a significant performance boost and reduces the size of the application.
Docker is a tool that is designed to benefit both developers and system administrators, making it a part of many DevOps (developers + operations) toolchains. For developers, it means that they can focus on writing code without worrying about the system that it will ultimately be running on.
OS-level virtualization refers to an operating system paradigm in which the kernel allows the existence of multiple isolated user space instances. Such instances, called containers (Solaris, Docker), Zones (Solaris), virtual private servers (OpenVZ), partitions, virtual environments (VEs), virtual kernel etc. Containers are isolated from one another and bundle their own software, libraries and configuration files; they can communicate with each other through well-defined channels. All containers are run by a single operating-system kernel and are thus more lightweight than virtual machines.
So, why does everyone love containers and Docker?
VM hypervisors, such as Hyper-V, KVM, and Xen, all are based on emulating virtual hardware. That means they need more resources.
On the othe rhand, Containers use shared operating systems. They are much more efficient than hypervisors in system resource terms. Instead of virtualizing hardware, containers rest on top of a single Linux instance. With a perfectly tuned container system, you can have as many as 4 times the number of server application instances as you can using Xen or KVM VMs on the same hardware.
Another reason why containers are popular is they lend themselves to Continuous Integration/Continuous Deployment (CI/CD).
Read more about Continuous Integration/Continuous Deployment (CI/CD) in this post: What Does It Mean By Continuous Integration, Continuous Delivery And Continuous Deployment?
Docker enables developers to easily pack, ship, and run any application as a lightweight, portable, self-sufficient container, which can run virtually anywhere. Containers do this by enabling developers to isolate code into a single container. This makes it easier to modify and update the program. In addition, Docker containers are easy to deploy in a cloud.
Specifically, for CI/CD Docker makes it possible to set up local development environments that are exactly like a live server; run multiple development environments from the same host with unique software, operating systems, and configurations; test projects on new or different servers; and allow anyone to work on the same project with the exact same settings, regardless of the local host environment. This enables developers to run the test suites, which are vital to CI/CD, to quickly see if a newly made change works properly.
What is Kubernetes?
Kubernetes is an open source orchestration system for automating the management, placement, scaling and routing of containers that has become popular with developers and IT operations teams in recent years.
It was first developed by Google and contributed to Open Source in 2014, and is now maintained by the Cloud Native Computing Foundation. Also known as “k8s,” Kubernetes provides automated container orchestration -- management of your machines and services for you -- improving your reliability and reducing the time and resources you need to spend on DevOps, not to mention relief from the stress attached to these tasks.
Kubernetes makes everything associated with deploying and managing your application easier. Kubernetes automates rollouts and rollbacks, monitoring the health of your services to prevent bad rollouts before things go bad. It also continuously runs health checks against your services, restarting containers that fail or have stalled, and only advertising services to clients when it has confirmed they’ve started up successfully. Additionally, Kubernetes will automatically scale your services up or down based off of utilization, ensuring you’re only running what you need, when you need it. Like containers, Kubernetes allows you to declaratively manage your cluster, allowing your setup to be version controlled and easily replicated.
- check Automated rollouts and roll backs
- check Service health monitoring
- check Automatic scaling of services
- check Declarative management
- check Deploy anywhere, including hybrid deployments
- Service and process definition
- Service discovery and load balancing
- Storage orchestration
- Container-level resource management
- Secrets and configuration management
We learned that Docker is a standalone software that can be installed on any computer to run containerized applications. Containerization is an approach of running applications on an OS such that the application is isolated from the rest of the system. Docker is what enables us to run, create and manage containers on a single operating system.
Kubernetes takes it further. If you have Docker installed on multiple hosts (different operating systems), you can leverage Kubernetes. Kubernetes can then allow you to automate container provisioning, networking, load-balancing, security and scaling across all these nodes from a single command line or dashboard. Kubernetes can work with any containerization technology
A collection of nodes that is managed by a single Kubernetes instance is referred to as a Kubernetes cluster.