rootfs_linux.go
func reOpenDevNull(rootfs string) error {
	var stat, devNullStat syscall.Stat_t
	file, err := os.Open("/dev/null")
	if err != nil {
		return fmt.Errorf("Failed to open /dev/null - %s", err)
	}
	defer file.Close()
	if err := syscall.Fstat(int(file.Fd()), &devNullStat); err != nil {
		return err
	}
	for fd := 0; fd < 3; fd++ {
		if err := syscall.Fstat(fd, &stat); err != nil {
			return err
		}
		if stat.Rdev == devNullStat.Rdev {
			// Close and re-open the fd.
			if err := syscall.Dup3(int(file.Fd()), fd, 0); err != nil {
				return err
			}
		}
	}
	return nil
}
func reOpenDevNull(rootfs string) error {
	var stat, devNullStat syscall.Stat_t
	file, err := os.Open("/dev/null")
	if err != nil {
		return fmt.Errorf("Failed to open /dev/null - %s", err)
	}
	defer file.Close()
	if err := syscall.Fstat(int(file.Fd()), &devNullStat); err != nil {
		return err
	}
	for fd := 0; fd < 3; fd++ {
		if err := syscall.Fstat(fd, &stat); err != nil {
			return err
		}
		if stat.Rdev == devNullStat.Rdev {
			// Close and re-open the fd.
			if err := syscall.Dup3(int(file.Fd()), fd, 0); err != nil {
				return err
			}
		}
	}
	return nil
}
// If stdin, stdout, and/or stderr are pointing to `/dev/null` in the parent's rootfs
// this method will make them point to `/dev/null` in this container's rootfs.  This
// needs to be called after we chroot/pivot into the container's rootfs so that any
// symlinks are resolved locally.