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This article introduces the relevant knowledge of "what are the basic Linux distributions for Docker?". In the operation of actual cases, many people will encounter such a dilemma. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Overview

The container-specific operating system refers to Linux distributions designed to run containers that provide some additional advantages in addition to regular distributions:

Simplicity: the container-specific operating system should be small and install only the necessary components. Minimize the number of accompanying tools and applications.

Atomic update.

By default, large-scale clusters can be built

The Docker daemon can be run automatically.

The root file system is read only.

Atomic updates can be rolled back (double partition update scheme).

Enhanced stability and security.

Based on these features, let's compare the common container Linux distributions: CoreOS,Ubuntu Snappy,Atomic,RancherOS and Photon.

These distributions are cloud native by default, and it provides a multiple distribution package that can be easily used for early initialization of cloud instances.

CoreOS

CoreOS is a cloud native distribution based on the Linux kernel that focuses on security, reliability, clustering, automation, and easy deployment. As a container operating system, CoreOS provides the functions needed to run the modern infrastructure stack, including the basic functional environment needed for the container to run, as well as a series of built-in tools for service discovery and shared configuration. CoreOS's policies and architecture allow users to run large-scale services with high resilience.

CoreOS comes with two container runtimes, such as Docker and Rocket, which can be automatically configured on each node. In addition, CoreOS provides automatic updates, and you can get all updates by default.

CoreOS uses its own built-in ignition as the starting point. Ignition is a configuration tool that runs at first startup and allows users to configure nodes in the same way. The preferred way to run applications on CoreOS is to run them in a container.

Etcd is also one of CoreOS's strengths. Etcd is a distributed key caching server, which is used by many projects such as Kubernetes,Cloud Foundry. You can use etcd for simple service discovery and so on.

Large cloud providers basically provide support for CoreOS.

CoreOS was acquired by Red Hat in 2018, and the upgraded version of Fedora CoreOS is the most important product and service in the current Red Hat Cloud strategy.

Flatcar Linux is a friendly open source branch of CoreOS Container Linux. Flatcar Linux is a direct substitute for Container Linux. The main idea behind Flatcar is to support Container Linux in a community-driven manner.

Ubuntu Core

Ubuntu Core is a mini-transactional version of Ubuntu for IoT devices and large container deployments. It runs a new super-secure, remotely upgradeable Linux application package, called snaps, which is supported and trusted by leading Internet of things vendors such as chipset manufacturers, device manufacturers and system integrators.

Ubuntu Core has built-in Canonical's AppArmor kernel security system to provide user-friendly security. Ubuntu Core allows applications to be completely isolated from each other for security.

Ubuntu Core can be easily extended through a so-called snap (such as Docker), and once a snap is added to Ubuntu Core, the application can be run on it.

All operating system and application files in Ubuntu Core remain separate and are read-only images. This makes updates on Ubuntu Core easy and predictable. Through incremental management, Ubuntu Core can minimize downloads. Ubuntu Core also provides rollback of system and application updates.

By default, Ubuntu Core does not have a built-in Docker runtime, but users can easily install Docker as a shortcut to running the Docker container. The installation is very simple:

Sudo snappy install docker

The first time you try Ubuntu Core, you need a Ubuntu account for the initial configuration of the ssh key.

RancherOS

The goal of the RancherOS project is to build a minimalist Linux distribution that allows Docker to run directly on top of the Linux kernel and distributes all user-space Linux services as Docker containers. This eliminates the need to use a separate package distribution mechanism for RancherOS itself.

In short, RancherOS is an OS made up of Containers, which runs the Docker daemon with PID 1, and the Docker daemon is the first process started by the kernel. There are two Docker daemons running in RancherOS, one for the system (System Docker) and one for the user (User Docker), and the system Docker is responsible for starting all system services, such as udev,DHCP and console. Therefore, RancherOS uses Docker as the initialization system and manages all system services as Docker containers.

One of the reasons RancherOS comes with two Docker daemons is that the system still works when the user accidentally stops / removes all containers from the user Docker.

When you run everything in a Docker container, the latest version of Docker is always available through RancherOS. You can easily extend RancherOS by running other system containers, for example, you can run your own console container to access your favorite console. Because the system is super compact, it has fewer security vulnerabilities and requires fewer patches, and provides higher stability.

Since all system services are delivered as Docker containers, there is no need for any package management tools such as apt-get or yum. Because the kernel and initrd are not Docker containers, RancherOS also uses Docker packaging and distribution to deliver kernel and initrd updates.

RancherOS can also be seen as a solution for embedded systems and IoT devices.

VMware Photon

Photon is the smallest technology preview version of the Linux container host. The design size of Photon is very small and can be started quickly on the VMware platform. Photon is designed to collaborate for containerized applications running in a virtualized environment.

VMware quickly creates a new operating system for containerized applications. VMware Photon is the smallest Linux container host optimized for vSphere. Photon supports all common Vmware Warden-based containers, such as Docker,rocket and Pivotal Garden container specifications. In addition, Photon comes with effective lifecycle management, which includes a yum-compatible package manager.

The main benefit of using Photon is VMware's Lightwave. Lightwave provides centralized identity management for authentication and authorization. It supports many open standards, such as LDAP,Kerberos,SAML and OAuth 2.0. Lightwave introduces container security to a new layer that supports centralized identity and access management.

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