How Docker containers works?

Have you ever wondered how Docker containers work?

First, lets make these things clear:

• VMs have their own kernel, making them heavier and slower compared to Docker containers.
• Docker containers share the host machine's kernel, making them lightweight and faster than VMs.
• There are different ways to create containers, but Docker is the most popular one (example: Podman, LXC, LXD, etc).
• A container must follow the OCI (Open Container Initiative) standards to be considered a container.

Now, lets see how (Docker Linux containers) works.

They are normal Linux processes that run in an isolated environment. And they rely on the following Linux features:

• Namespaces: This keeps each container separate from the others. It isolates things like processes, network, user IDs, and file systems, but they still share the same basic system (kernel).
• Control groups (cgroups): These control and limit how much of the computer's resources (like CPU, memory, disk, and network) each container can use. It helps in managing and isolating resource usage for a group of processes.

So, now what happens when you execute a command like docker run -it ubuntu bash?

• Docker will create a new container process.
• a new namespace will be created for the container.
• a new cgroup will be created for the container.
• a new root filesystem will be created for the container.
• a new network interface will be created for the container.

Resources:

• What Is a Standard Container