Why does docker start so fast

The reason why Docker starts so quickly: Docker container applications run directly in the host kernel. Starting Docker is equivalent to starting a process on the host operating system without starting a complete operating system; therefore, it can be done in seconds. Level, even millisecond startup time.

The operating environment of this tutorial: linux5.9.8 system, docker-1.13.1 version, Dell G3 computer.

Docker allows developers to package their applications and dependencies into a portable container and then publish it to any popular Linux machine, which can be virtualized. Docker has changed the way of virtualization, allowing developers to directly put their results into Docker for management. Convenience and speed are already the biggest advantages of Docker. Tasks that used to take days or even weeks can be completed in just a few seconds under the processing of Docker containers.

Why does docker start so fast?

Starting a virtual machine requires first starting the virtual machine's operating system and then starting the application. This process is very slow and often takes several minutes.

As for the docker container application, since it runs directly in the host kernel, starting Docker is equivalent to starting a process on the host operating system without starting the complete operating system; therefore, it can be started in seconds or even milliseconds. time, greatly saving development, testing, and deployment time.

Advantages of container (Docker) compared to virtual machine (VM):

##ConcurrencyA host can start thousands or hundreds of containersUp to dozens of virtual machinesPerformanceClose to the local host Processis worse than the hostResource utilizationHighLow

	Container technology	Virtual machine technology
Occupied disk space	Small, even dozens of KB (in the case of the mirror layer)	Very large , on GB
Startup speed	Fast, a few seconds	Slow, a few minutes
Running form	Run directly on the kernel of the host, different containers share the same Linux kernel	Run on Hypervisior

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