Kubernetes Container Definition
Kubernetes is an open-source, extensible, portable container management platform. Kubernetes has a sizable ecosystem that is designed for facilitating both automation and declarative configuration and managing containerized workloads and services.
What is a container in Kubernetes? Kubernetes containers resemble virtual machines (VMs), each with its own CPU share, filesystem, process space, memory, and more. However, Kubernetes containers are considered lightweight because:
- they can share the Operating System (OS) among applications due to their relaxed isolation properties
- they are decoupled from the underlying infrastructure
- they are portable across OS distributions and clouds
Each running Kubernetes container is repeatable. Users can expect the same behavior from a Kubernetes container regardless of its environment because included dependencies standardize performance.
Decoupling applications from underlying host infrastructure makes it simpler to deploy in various OS or cloud environments.
Kubernetes Containers FAQs
Wha are Kubernetes Containers?
What are containers in Kubernetes? Before containers, users typically deployed one application per virtual machine (VM), because deploying multiple applications could trigger strange results when shared dependencies were changed on one VM. Essentially, Kubernetes containers virtualize the host operating system and isolate the dependencies of an application from other running containers in the same environment.
Running a single application for each VM resolves this issue, but wastes CPU and memory resources that should be available to the application. Kubernetes containers instead use a container engine to run applications that can all use the same operating system in containers isolated from other applications on the host VM. Kubernetes containers also use a container image, a ready-to-run software package of an application and its dependencies that contains everything needed to run an application: code, required runtime, system and application libraries, and essential setting default values. This reduces costs and allows for higher resource utilization.
Benefits of Kubernetes Containers
Kubernetes containers offer a number of benefits, including:
- Agile creation and deployment of applications and container images compared to VMs
- Image immutability allows for more frequent, reliable container image build and efficient, speedy rollbacks during deployment
- Development and Ops concerns decoupled with infrastructure and applications as container images are created at build/release time rather than deployment time
- Enhanced observability of OS-level metrics and application health
- Environmental consistency across machines and clouds through development, testing, and production
- Portable distribution on major public clouds, on-premises, on CoreOS, RHEL, Ubuntu, and elsewhere
- Runs application using logical resources on an OS for application-centric focus
- Distributed, dynamic microservices application environment contrasts with larger single-purpose machine running a monolithic stack
- Resource isolation results in predictable performance
- High resource utilization and density
Kubernetes containers support an extremely diverse variety of workloads, including stateful and stateless applications and data-processing workloads. Kubernetes containers can run any container applications.
Furthermore, Kubernetes eliminates the need for orchestration or centralized control. Kubernetes includes multiple, independent control processes that drive the system towards the desired state continuously regardless of the specific order of steps. This produces a more dynamic, extensible, powerful, resilient, and robust system that is more user-friendly.
What Are Containers and Kubernetes and How Do They Work?
Kubernetes comprises several components deployed as a cluster that interact together. A Kubernetes container cluster serves as the basic Kubernetes architecture and a sort of motherboard or central nervous system orchestrating applications and running pods as defined by users.
A Kubernetes container uses a Kubernetes container runtime and runs logically in a pod and houses the cluster. A group of pods run on a cluster, whether related or not. Nodes, physical or virtual machines that exist between the pod and cluster, host the pods.
Each Kubernetes container cluster is made up of at least one worker node, worker machines that run containerized applications. The control plane manages the Kubernetes pods and worker nodes in the cluster.
Control plane components include:
kube-apiserver: the API server is the front end for the Kubernetes control plane and exposes the Kubernetes API. The kube-apiserver is designed to scale by deploying more instances, horizontally—traffic balances between the instances.
etcd: the etcd is a highly-available, consistent key value store for all cluster data.
kube-scheduler: kube-scheduler assigns newly created pods to nodes based on affinity and anti-affinity specifications, deadlines, data locality, hardware/software/policy constraints, individual and collective resource requirements, and inter-workload interference.
kube-controller-manager: the kube-controller-manager runs each separate controller process by compiling them into one single process to reduce complexity.
cloud-controller-manager: cloud-controller-manager links cloud APIs and clusters with cloud-specific control logic to enable interactions.
kubectl: kubectl allows users to run Kubernetes container commands against clusters. It is installable on Windows, macOS, and a variety of Linux platforms. kubectl can help users inspect and manage cluster resources, deploy applications, and view logs.
kubelet: kubelet runs on all cluster nodes to ensure containers in a pod are running and healthy.
kube-proxy: kube-proxy runs on each cluster node, maintaining network communication rules and implementing the Kubernetes Service concept.
Kubernetes container runtime: Kubernetes container runtime is the software implementation of the Kubernetes CRI (Container Runtime Interface) that runs containers. Kubernetes supports many container runtimes, including containerd, Docker Engine, CRI-O, and Mirantis Container Runtime. Docker is the most frequently used Kubernetes container runtime, which is why some Kubernetes container management discussion does include general Docker terms.
Docker Container vs Kubernetes
It may be tempting to make a Kubernetes container vs Docker container comparison, because both present comprehensive container management solutions for applications with impressive capabilities. However, they have different origins, solve different problems, and are therefore not precisely comparable.
Here are a few differences:
- Kubernetes is designed to run across a cluster, in contrast to Docker, which runs on a single node
- Kubernetes needs a container runtime to orchestrate, while Docker can be used without Kubernetes
- Kubernetes is designed to include custom plugins that build out into custom solutions, while it is simple to run a Docker build on a Kubernetes cluster
- Both Kubernetes and Docker Swarm are orchestration technologies, but Kubernetes is agnostic about ecosystems while Docker Swarm is closely integrated with the Docker ecosystem
- Kubernetes has become the container management and orchestration de facto standard, while Docker has become better-known for container development and deployment
Does Avi Offer Kubernetes Container Monitoring?
Yes. Avi Vantage delivers multi-cloud application services such as load balancing for containerized applications with microservices architecture through dynamic service discovery, application traffic management, and web application security. Container Ingress provides scalable and enterprise-class Kubernetes ingress traffic management, including local and global server load balancing (GSLB), web application firewall (WAF) and performance monitoring, across multi-cluster, multi-region, and multi-cloud environments. Avi integrates seamlessly with Kubernetes for container and microservices orchestration and security.
Learn more about the universality, security, and observability of Avi’s Kubernetes container monitoring solution.
For more on the actual implementation of load balancing, security applications and web application firewalls check out our Application Delivery How-To Videos.