Docker second round (use of Docker)

I. restrictions on the use of Docker

1. To use the linux container, the kernel version should be higher than 3.8, and at least two technologies, namespaces and CGroups, should be supported at the linux kernel level. Then, with the help of organizing some tools in user space and making use of these technologies provided by the kernel level, so as to achieve the purpose of container operation, Docker is one step closer on the way of simplifying the operation and use of containers. Docker provides mirroring, and it is a way of hierarchical construction and joint mounting, which makes the use of container technology more simplified. Later, under the leadership of Docker, there were OCI and OCF standards.

OCI (Open Container Initiative): created in June 2015 under the leadership of the Linux Foundation, OCI defines the standard for container runtime

OCI consists of two parts:

The Runtime Specification: runtime standard

The image Specification: image format standard

OCF (Open Container Format): runC is a specific implementation developed by Docker in accordance with the Open Container format Standard (OCF). RunC is migrated from Docker's libcontainer to achieve container start and stop, resource isolation and other functions. Docker provides docker-runc implementation by default.

Second, the image of Docker

By default, the image of Docker is centrally placed on Docker Hub. When docker creates a container, Docker will first check whether there is an image locally. If it does not download the specified image to the local place on docker hub, and the downloaded image will not be deleted after the use of the container, the image cannot be modified and can only be reconstructed. Here is the overall architecture of docker