What is runc in docker

In docker, RunC is a CLI tool that creates and runs containers according to OCI standards. It is a command line tool that follows OCI standards for running containers. runC is the core part of docker. The creation, running, destruction and other operations of the container will eventually be completed by calling runc.

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

OCI defines the container runtime standard, and runC is a specific implementation formulated by Docker in accordance with the open container format standard Open Container Format, OCF.

This project is migrated from Docker's libcontainer and implements functions such as container start and stop, resource isolation, etc. Therefore, the container can be run directly through this tool.

Introduction

The so-called container runtime (Container Runtime) includes container management and container imaging. Open Container Initiative, OCI is the industry standard for container runtime, including:

A) Runtime standard runtime-spec;

B) Container image standard image-spec.

Simply put, the container image standard defines the packaging form of the container image, and the runtime standard defines how to run a container.

RunC is a CLI tool that creates and runs containers according to OCI standards. It is a command line tool for running containers that follows OCI standards. It is also a Runtime implementation.

Docker

In the old version, you need to call docker-runc, but in the latest CE version, directly Modified to runc command.

#RunC is the bottom-level running environment of the container, and its upper layer is managed through Docker.

runC is the core part of docker. The creation, running, destruction and other operations of the container will eventually be completed by calling runc.

Independent operation

RunC is the running state of the container and does not include image management. If you use it directly, you need to prepare the image first. Here, you can directly use the already built BusyBox template.

OCI Bundle

OCI Bundle refers to a series of files that meet OCI standards. These files contain all the data needed to run the container. They are stored in a common directory, which contains the following two items:

• config.json Contains the configuration data of the container running;
• The root filesystem of the container .

If Docker is installed on the host, you can use the docker export command to export the existing image into OCI Bundle format.

Generate rootfs

Use the BusyBox template in Docker directly.

----- 下载最新的版本
$ docker pull busybox

----- 创建rootfs
$ mkdir rootfs
$ docker export $(docker create busybox) | tar -C rootfs -xvf -

Configuration file

In the rootfs directory, it contains common binary files , in addition to the root directory, a config.json configuration file is also required, and the configuration template can be generated through the runc spec command.

For detailed configuration, please refer to https://github.com/opencontainers/runtime-spec/blob/master/spec.md

Change "terminal" in the configuration file: true is changed to false, otherwise cannot allocate tty if runc will detach without setting console socket will be reported when creating.

In addition, because the terminal is closed, the command is modified to "args": [ "sleep", "10000" ], parameters.

Start

----- 创建容器并查看状态
# runc create mybusybox
# runc list

----- 启动容器，并查看状态
# runc start mybusybox

----- 删除容器
# runc delete mybusybox

After starting, you can passps aux | grep sleep See specific commands.

Common commands

----- 查看容器状态
# runc state mybusybox

----- 容器内运行进程
# runc ps mybusybox

----- 在容器中执行命令
# runc exec mybusybox ls

----- 停止容器内的任务
# runc kill mybusybox

----- 暂停容器内的所有进程
# runc pause mybusybox

----- 恢复容器内进程的执行
# runc resume mybusybox

----- 获取容器的资源使用情况
# runc events mybusybox

Hot migration

is to perform a CheckPoint operation on a container and obtain a series of files, and then start it on other machines .

Recommended learning: "docker video tutorial"

The above is the detailed content of What is runc in docker. For more information, please follow other related articles on the PHP Chinese website!