While learning about Docker, I wanted to understand exactly why containers are so much lighter than Virtual Machines (VMs).
If you don't know what a VM is, it’s basically like a computer inside a computer. You have your physical hardware and your main Operating System (OS). To run another computer inside it, you use a Hypervisor.
The problem is that a VM is heavy. It has its own separate hardware, its own software, and its own full OS. This is why a VM takes a long time to boot up and uses a lot of hardware resources.
On the other side, Docker containers are light and fast. Here is why:
Sharing the Kernel: Containers don't need their own OS. They use the host kernel (the brain of the OS already running on your laptop), which makes them much smaller.
Images are Read-Only: A Docker image is just a read-only blueprint. When you start a container, you are just adding a thin, writable layer (a wrapper) on top of that image.
Smart Space Usage: If you have an image that is 500MB and you create 10 containers from it, they don't take up 5GB. They still only use 500MB because they all share that same base image.
Because the container layer is the only writable part, it is temporary. This is exactly where Volumes come in. We use volumes to store important things like source code or databases so the data stays safe even if the container is deleted.
Understanding this difference helps you see why we use containers to move fast and save space.
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