手把手教你玩转 Docker

Markgogogo

发布于 2022-06-13 15:14:45

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文章被收录于专栏：3分钟云计算

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程序员最爱说的是：“ 我这本地运行的好好的，怎么在客户那就不行了呢！”

关于Docker 的文章和相关书籍非常繁多，从Docker 的概念，架构，到容器的编排管理等等，内容很多。但是对于非运维人员来说，其实一篇文章就够了，那些书籍，可以当作工具书使用，需要的时候再去查。

本文将给出一个简单的例子，带你轻松了解Docker到底是做什么的，为啥如今这么火？

1，安装Docker

此部分略过，你买的Docker书籍上都有，估计得占了一个章节，如果你之前有过Linux 相关经验，一条指令的事。本示例基于Red Hat Fedora 28, Docker 19. 如下：

[jzhang@dhcp-140-36 show]$ cat /etc/redhat-release 
Fedora release 28 (Twenty Eight)
[root@preserve-olm-env data]# docker version
Client: Docker Engine - Community
 Version:           19.03.9
 API version:       1.40
 Go version:        go1.13.10
 Git commit:        9d988398e7
 Built:             Fri May 15 00:25:27 2020
 OS/Arch:           linux/amd64
 Experimental:      false

当你安装好Docker后，会生成一个可执行文件，也叫docker. 查看帮助信息，指令很多，但是，别慌～日常使用，也就会用到那几个而已

[root@preserve-olm-env data]# which docker
/usr/bin/docker
[root@preserve-olm-env data]# docker --help

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:
      --config string      Location of client config files (default "/root/.docker")
  -c, --context string     Name of the context to use to connect to the daemon (overrides DOCKER_HOST env var and default context set
                           with "docker context use")
  -D, --debug              Enable debug mode
  -H, --host list          Daemon socket(s) to connect to
  -l, --log-level string   Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
      --tls                Use TLS; implied by --tlsverify
      --tlscacert string   Trust certs signed only by this CA (default "/root/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default "/root/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default "/root/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Management Commands:
  builder     Manage builds
  checkpoint  Manage checkpoints
  config      Manage Docker configs
  container   Manage containers
  context     Manage contexts
  engine      Manage the docker engine
  image       Manage images
  network     Manage networks
  node        Manage Swarm nodes
  plugin      Manage plugins
  secret      Manage Docker secrets
  service     Manage services
  stack       Manage Docker stacks
  swarm       Manage Swarm
  system      Manage Docker
  trust       Manage trust on Docker images
  volume      Manage volumes

Commands:
  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  deploy      Deploy a new stack or update an existing stack
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

Run 'docker COMMAND --help' for more information on a command.

2，编写一个简单程序。Golang 代码，输出 Hello Docker! 如下，

package main

import (
  "fmt"
  "net/http"
)

func main() {
  http.HandleFunc("/docker", handleDocker)
  http.ListenAndServe(":8080", nil)
}

func handleDocker(w http.ResponseWriter, r *http.Request) {
  fmt.Fprintln(w, "Hello Docker!")
}

编译运行，我是在一个虚拟机上运行的。

[jzhang@dhcp-140-36 show]$ export CGO_ENABLED=0
[jzhang@dhcp-140-36 show]$ go build
[jzhang@dhcp-140-36 show]$ ls
main.go  show
[jzhang@dhcp-140-36 show]$ ./show

在浏览器窗口输入http://10.66.140.36:8080/docker 效果如下：

3，容器化，也就是把这个程序放到容器中去运行

编写Dockerfile，具体的FROM, Add, CMD 等指令可以参考那些工具书，这里略过。

[jzhang@dhcp-140-36 show]$ ls
Dockerfile  main.go  show
[jzhang@dhcp-140-36 show]$ cat Dockerfile 
FROM scratch
Add show /
CMD ["/show"]

创建Docker 镜像

[jzhang@dhcp-140-36 show]$ docker build -t quay.io/jiazha/show:v1 .
Sending build context to Docker daemon  7.399MB
Step 1/3 : FROM scratch
 ---> 
Step 2/3 : Add show /
 ---> e1d83a8ffad9
Step 3/3 : CMD ["/show"]
 ---> Running in 8a13dafb50df
Removing intermediate container 8a13dafb50df
 ---> 55ccf78c9a91
Successfully built 55ccf78c9a91
Successfully tagged quay.io/jiazha/show:v1

查看镜像大小，才7M 左右，相当nice~

[jzhang@dhcp-140-36 show]$ docker image ls quay.io/jiazha/show:v1
REPOSITORY            TAG                 IMAGE ID            CREATED             SIZE
quay.io/jiazha/show   v1                  55ccf78c9a91        4 minutes ago       7.39MB

4, 容器化运行

因为现在show 可执行文件是在镜像中了，所以运行它时，使用的是容器的8080端口，并不是之前的那台虚拟机的。我们来看下，

[jzhang@dhcp-140-36 show]$ docker run  quay.io/jiazha/show:v1

docker ps 查看该容器ID.

[jzhang@dhcp-140-36 ~]$ docker ps
CONTAINER ID        IMAGE                    COMMAND             CREATED             STATUS              PORTS               NAMES
61326acc97fb        quay.io/jiazha/show:v1   "/show"             8 seconds ago       Up 7 seconds                            kind_haibt

docker inspect 指令查看该容器IP 地址

[jzhang@dhcp-140-36 ~]$ docker inspect 61326acc97fb --format='{{.NetworkSettings.IPAddress}}'
172.17.0.2

curl 指令检查 show 是否在容器中正常运行

[jzhang@dhcp-140-36 ~]$ curl 172.17.0.2:8080/docker
Hello Docker!

输出Hello Docker! Prefect！
补充：那如何访问改虚拟机端口来获取输出呢？可以使用端口映射，如下，把容器的8080端口映射到虚拟机的80端口

[jzhang@dhcp-140-36 show]$ docker run  -p 80:8080 quay.io/jiazha/show:v1

打开浏览器访问虚拟的8080端口，预期失败。

改为访问80端口，成功。

到此，程序容器化已经完成了，是不是很简单？

5, 发布该镜像

我是用的是Red Hat 的quay.io 镜像仓库，跟dockerhub一样，主要是镜像的托管服务，漏洞检测等。把镜像推送到名叫jiazha的registry.

[jzhang@dhcp-140-36 show]$ docker push quay.io/jiazha/show:v1
The push refers to repository [quay.io/jiazha/show]
ce5f0c851050: Pushed 
v1: digest: sha256:f052362823506b97b738ba48d4227981758936fd1c6c30ab69e76492825b3243 size: 528

6, 换个平台，运行show 镜像，这里使用的是Mac

下载上边发布的镜像，然后运行，映射到本地8083端口。

mac:~ jianzhang$ docker pull quay.io/jiazha/show:v1
v1: Pulling from jiazha/show
038b2980cdca: Pull complete 
Digest: sha256:f052362823506b97b738ba48d4227981758936fd1c6c30ab69e76492825b3243
Status: Downloaded newer image for quay.io/jiazha/show:v1
mac:~ jianzhang$ docker run  -p 8083:8080 quay.io/jiazha/show:v1