As a beginner trying to grasp Kubernetes, I've been mapping out the internal architecture of a basic K8s setup using a local path provider and flannel. I've noticed that K8s uses a lot of "containers" for core operations, like how kube-proxy interacts with the host's ip-table. I'm curious how experts would define what a container inside a pod actually is. Can I compare them to AWS Lambda or Azure Functions, where they execute small pieces of code quickly and terminate? However, I think these functions still come with a ready-to-deploy container that includes an OS. What are the real differences?
5 Answers
Containers inside a pod are essentially just containers running packaged applications. For example, in the case of kube-proxy, the container's job is to manage network changes directly on the host's system.
It sounds like you're curious about how container images are built. Containers actually operate differently from virtual machines. They share the host's kernel, so even if you use an image like ubuntu:latest, it doesn't function as a full OS. Plus, the containers you're seeing are really optimized to have minimal overhead, so they're designed for fast and efficient tasks.
On a basic level, containers create a mild separation between processes. Think of it like different rooms in a house, where each room can have its own setup without interfering with others. They maintain their own namespaces for things like processes and file systems. When you run a program in a language like Go, it often has everything it needs bundled together, which is why it can be somewhat larger to launch, while older programs might need a lot of extra files. When you're running containers, it’s essential to minimize those dependencies for efficiency.
That’s a neat way to put it! I didn’t realize how much the languages and their requirements affect container size and efficiency.
Many Kubernetes components use what’s called distroless images, or sometimes even have no OS at all, just a statically linked binary. These are super lightweight and designed to minimize overhead, which is perfect for what K8s needs.
Contemplating the isolation features of containers might help! Although they can share some resources like the network, each container in a pod operates within its own defined namespaces. This means some processes can notably look independent. For instance, a Go app might run with just its binary, while Nginx needs quite a bit more to operate properly. So, yes, you could describe Lambda and Azure Functions as single-use containers.
Yeah, it's really interesting how much efficiency they bring! I think understanding container isolation can help clarify things further.