main.go

package main

import (
	"flag"
	"fmt"
	"os"
	"os/exec"
	"syscall"

	"github.com/docker/docker/pkg/reexec"
)

func init() {
	reexec.Register("InitContainer", InitContainer)
	if reexec.Init() {
		os.Exit(0)
	}
}

func InitContainer() {
	newrootPath := os.Args[1]

	if err := mountProc(newrootPath); err != nil {
		fmt.Printf("Error mounting /proc - %s\n", err)
		os.Exit(1)
	}

	if err := pivotRoot(newrootPath); err != nil {
		fmt.Printf("Error running pivot_root - %s\n", err)
		os.Exit(1)
	}

	if err := cgroup(); err != nil {
		fmt.Printf("Error running cgroup - %s\n", err)
		os.Exit(1)
	}

	Run()
}

func Run() {
	cmd := exec.Command("/bin/sh")

	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	cmd.Env = []string{"PS1=-[shoten]- # "}

	if err := cmd.Run(); err != nil {
		fmt.Printf("Error running the /bin/sh command - %s\n", err)
		os.Exit(1)
	}
}

func main() {
	var rootfsPath string
	flag.StringVar(
		&rootfsPath,
		"rootfs",
		"/tmp/shoten/rootfs",
		"Path to the root filesystem to use",
	)
	flag.Parse()

	cmd := reexec.Command("InitContainer", rootfsPath)
	cmd.SysProcAttr = &syscall.SysProcAttr{
		Cloneflags: syscall.CLONE_NEWUSER |
			syscall.CLONE_NEWNET |
			syscall.CLONE_NEWPID |
			syscall.CLONE_NEWIPC |
			syscall.CLONE_NEWUTS |
			syscall.CLONE_NEWNS,
		UidMappings: []syscall.SysProcIDMap{
			{
				ContainerID: 0,
				HostID:      os.Getuid(),
				Size:        1,
			},
		},
		GidMappings: []syscall.SysProcIDMap{
			{
				ContainerID: 0,
				HostID:      os.Getgid(),
				Size:        1,
			},
		},
	}

	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	if err := cmd.Run(); err != nil {
		fmt.Printf("Error running the reexec.Command - %s\n", err)
		os.Exit(1)
	}
}