The Story.

In the bad old days, businesses used to run one application per Windows or Linux server—a costly approach that wasted both money and resources.

Then came VMware, and everything changed. For the first time, multiple applications could run on a single physical server. While this was a huge step forward, it wasn’t perfect. Virtual machines are slow to boot, consume large amounts of RAM and CPU, and are often hard to migrate and maintain.

Hello Containers, Companies like Google had been using container technologies internally for years to overcome the limitations of traditional virtual machines. Unlike VMs, containers don’t require a full operating system for each application. Instead, they share the host OS, making them lighter, faster..

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Google LLC, has contributed a lot in the container related technologies, thank you google 😊

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But Containers remained complex and out of reach, till Docker came and democratized this technologies.

Docker.Inc Made Containers simple

The Big Picture.

Docker Inc, a technology based company started in San Francisco.

Docker the technology.

• The Runtime (the lowest level)
• The Daemon (Docker Engine)
• The orchestrate

Main focus is managing and running application containers, and it can basically anywhere.

When you install docker you get two components

• The Docker Client: The client talk to the daemon via a local IPC/Unix Socket in /var/run/docker.sock and in windows happened via named pipe.
• The Docker Engine: It implement the runtime, API…

The Technical Stuff.

The Docker engine is the core software that runs and manages containers, it is modular is design and built from many small tools, and that was possible because they were based on open standards such as those maintained by Open Container Initiative (OCI), its a is an open governance structure for the express purpose of creating open industry standards around container formats and runtimes.

• runc is a small lightweight CLI wrapper for libcontainer, its only purpose its to create containers, its is very low level, bare bones.
• containerd is available as daemon for linux and windows, its purpose is to manage containers life-cycle operations such as start | stop | pause | rm…
• Namespaces: Provide isolation. Each container gets its own view of the system (PID for processes, NET for networking, MNT for the filesystem).
• Control Groups (cgroups): Provide resource limits. They prevent a single container from eating all the host’s CPU or RAM.

Docker is not a monolithic program; it is a modular system built on top of Linux kernel features.