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On the development history of containers

With regard to the historical stories that containers have to tell, the following information comes from Internet collection:

The concept of container began with UNIX chroot, which was put forward in 1979. It is a system call of UNIX operating system, which changes the root directory of a process and its children to a new location in the file system, so that these processes can only access this new location, thus achieving the purpose of process isolation.

In 2000, FreeBSD developed a container technology similar to chroot, Jails, which is the earliest and most versatile container technology. Jails translates into English to mean prison, which (more accurately sandboxie) includes the isolation of file systems, users, networks, processes, etc.

2001 Linux also released its own container technology, Linux VServer,2004 Solaris, and released Solaris Containers, both of which divide resources into zones, also known as virtual servers.

OpenVZ was launched in 2005 to provide virtualization support through patches to the Linux kernel, with each OpenVZ container fully supporting the isolation of file systems, users and user groups, processes, networks, devices, and IPC objects.

In 2007, Google implemented Control Groups (cgroups) and added it to the Linux kernel, which is epoch-making and provides a technical guarantee for later container resource quotas.

In 2008, the first most complete Linux container, LXC, was launched based on cgroups and linux namespace.

The most popular and widely used container Docker was launched in 2013. Compared to other early container technologies, Docker introduces a complete set of container-managed ecosystems, including a hierarchical mirror model, container registry, and friendly Rest API.

In 2014, CoreOS also introduced a container similar to Docker, Rocket,CoreOS, a more lightweight Linux operating system that is more secure than Docker.

Microsoft also provided container support on Windows in 2016, and Docker can run natively on Windows instead of using a Linux virtual machine.

The difference between container and virtual machine

On the left is the virtual machine and on the right is the container. From the sense, the virtual machine has more layers than the container, with one more operating system. On the other hand, the container is encapsulated on the original operating system by using related technologies such as resource isolation, and the container is isolated from each other in the application layer, which achieves the effect of isolation between virtual machines with less performance loss than virtual machines. The way of the virtual machine is not useless, the virtual machine has its own advantages, for example, it carries and isolates multiple operating system instances in the upper layer, which is more in line with the running mechanism of the computer, and the cost of program code migration is also lower. containers often need a certain amount of technology accumulation in order to do a good job of mirroring the container. Generally speaking, there is no absolute difference between the pros and cons of the plan, and only the one that best suits your needs is a good one.

Characteristics of containers

In a word, summarize the characteristics of the container: Build   once,Run   anywhere! (once built, it can be used everywhere)

The three core concepts of Docker technology are:

● Mirror (Image)

● container (Container)

● warehouse (Repository)

These will be described in detail in subsequent practical articles, as well as more advantages and convenience of containers.

I have to say, K8S

Kubernetes (K8s for short, an abbreviation for 8 instead of 8 characters "ubernete") is an open source container orchestration engine for Google. Since there is a popular docker product, why does it derive a K8s that is favored by many cloud vendors and withdraw from its own container service DaaS on the basis of K8s? we have to say the characteristics of K8s:

● coordinates auxiliary processes, assists in application integration, and maintains an one-to-one "program-mirror" model.

● mount storage system

● distributed secret information

● checks program status

● replication application instance

● uses horizontal pod auto scaling

Naming and Discovery of ●

● load balancing

● rolling update

● resource monitoring

● accesses and reads logs

● program debugging

● provides authentication and authorization

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