自己动手写 Docker 系列 -- 5.8 实现容器制定环境变量运行

var RunCommand = cli.Command{  Name:  "run",  Usage: `Create a container with namespace and cgroups limit mydocker run -ti [command]`,  Flags: []cli.Flag{    ......    cli.StringSliceFlag{      Name:  "e",      Usage: "set environment",    },  },  /*    这里是run命令执行的真正函数    1.判断参数是否包含command    2.获取用户指定的command    3.调用Run function 去准备启动容器  */  Action: func(context *cli.Context) error {    ......    // 获取并传入    envSlice := context.StringSlice("e")    run.Run(tty, detach, cmdArray, resConfig, volume, containerName, envSlice)    return nil  },}

func Run(tty, detach bool, cmdArray []string, config *subsystem.ResourceConfig, volume, containerName string, envSlice []string) {  ......  parent, writePipe := container.NewParentProcess(tty, containerName, rootUrl, mntUrl, volume, envSlice)  if err := parent.Start(); err != nil {    log.Error(err)    // 如果fork进程出现异常，但有相关的文件已经进行了挂载，需要进行清理，避免后面运行报错时，需要手工清理    deleteWorkSpace(rootUrl, mntUrl, volume, containerName)    return  }  ......}

func NewParentProcess(tty bool, containerName, rootUrl, mntUrl, volume string, envSlice []string) (*exec.Cmd, *os.File) {  ......    // 将管道的一端传入fork的进程中  cmd.ExtraFiles = []*os.File{readPipe}  if err := newWorkSpace(rootUrl, mntUrl, volume, containerName); err != nil {    log.Errorf("new work space err: %v", err)    return nil, nil  }  cmd.Dir = mntUrl  // 直接添加环境变量到系统中  cmd.Env = append(os.Environ(), envSlice...)  return cmd, writePipe}

func ExecContainer(containerName string, commandArray []string) error {  ......
  // 获取环境变量，重新注入  envs, err := getEnvsByPid(pid)  if err != nil {    return err  }  cmd.Env = append(os.Environ(), envs...)
  if err := cmd.Run(); err != nil {    return fmt.Errorf("exec container %s err: %v", containerName, err)  }  return nil}

func getEnvsByPid(pid string) ([]string, error) {  path := fmt.Sprintf("/proc/%s/environ", pid)  contentBytes, err := ioutil.ReadFile(path)  if err != nil {    return nil, fmt.Errorf("read file %s err: %v", path, err)  }  return strings.Split(string(contentBytes), "\u0000"), nil}

root@lw-Code-01-Series-PF5NU1G  ~/code/go/dockerDemo   main ● ↑1  go build mydocker/main.go                                                                               SIG(127) ↵  ⚡  513  06:35:19root@lw-Code-01-Series-PF5NU1G  ~/code/go/dockerDemo   main ● ↑1  ./main run -ti -e bird=123 sh                                                                                    ✔  ⚡  514  06:35:21{"level":"info","msg":"memory cgroup path: /sys/fs/cgroup/memory/mydocker-cgroup","time":"2022-04-14T06:35:28+08:00"}{"level":"info","msg":"memory cgroup path: /sys/fs/cgroup/memory/mydocker-cgroup","time":"2022-04-14T06:35:28+08:00"}{"level":"info","msg":"all command is : sh","time":"2022-04-14T06:35:28+08:00"}{"level":"info","msg":"parent process run","time":"2022-04-14T06:35:28+08:00"}{"level":"info","msg":"init come on","time":"2022-04-14T06:35:28+08:00"}{"level":"info","msg":"current location: /home/lw/code/go/dockerDemo/mnt","time":"2022-04-14T06:35:28+08:00"}{"level":"info","msg":"find path: /bin/sh","time":"2022-04-14T06:35:28+08:00"}/ # env |grep birdbird=123/ # exit
 root@lw-Code-01-Series-PF5NU1G  ~/code/go/dockerDemo   main ● ↑1  ./main run -d -e bird=123 -name bird top                                                                SIG(127) ↵  ⚡  515  06:35:58{"level":"info","msg":"memory cgroup path: /sys/fs/cgroup/memory/mydocker-cgroup","time":"2022-04-14T06:36:14+08:00"}{"level":"info","msg":"memory cgroup path: /sys/fs/cgroup/memory/mydocker-cgroup","time":"2022-04-14T06:36:14+08:00"}{"level":"info","msg":"all command is : top","time":"2022-04-14T06:36:14+08:00"}{"level":"info","msg":"parent process run","time":"2022-04-14T06:36:14+08:00"}root@lw-Code-01-Series-PF5NU1G  ~/code/go/dockerDemo   main ● ↑1  ./main exec bird env |grep bird                                                                         SIG(127) ↵  ⚡  516  06:36:15bird=123