What a Linux container really is (it's not a VM)
Right now, on your machine, a process is being lied to . It thinks it's alone on the computer. It thinks it owns the whole filesystem. It thinks its process ID is 1 . None of that is true. It's running right next to everything else, on the same kernel — and the kernel is lying to its face. That lie has a name. We call it a container . Prefer to watch? Full 6-minute walkthrough with the animation:…
A Linux container is not a virtual machine (VM), but rather a process running on the same kernel as other processes on the host machine. This container is created by altering the process's view of the system, through the use of namespaces, and its use of system resources, via control groups (cgroups). Namespaces are what the process can see, while cgroups determine what resources it can utilize.
This setup allows multiple containers to run on a single host, each with its own isolated environment while sharing the same kernel. A container does not have its own kernel, nor does it encapsulate its own operating system. Instead, it is a single process wrapped in these two key features. The misconception often arises from visual representations of containers as separate entities, but in reality, they are just normal processes with their environment managed by the kernel.
Docker, for instance, accomplishes this by unpacking the container image, applying namespaces, applying cgroups, and then executing the process. The container image itself is merely a collection of files and metadata, not an operating system or a kernel. This setup enables containers to start up much faster than VMs, which must boot their own operating system and kernel, making containers a more efficient solution for many use cases.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
