Add support for "run in"

To support "exec" health checking, debugging and kubelet lifecycle events
Run as root?

----- Original Message -----
> > @@ -63,6 +64,30 @@ func NewDockerPuller(client DockerInterface)
> > DockerPuller {
> >  	}
> >  }
> >  
> > +type dockerContainerCommandRunner struct{}
> > +
> > +func (d *dockerContainerCommandRunner)
> > getRunInContainerCommand(containerID string, cmd []string) (*exec.Cmd,
> > error) {
> > +	args := append([]string{"exec"}, cmd...)
> > +	command := exec.Command("/usr/sbin/nsinit", args...)
> > +	command.Dir = fmt.Sprintf("/var/lib/docker/execdriver/native/%s",
> > containerID)
> 
> Trying to manual repro this, so I understand it, I get an error:
> 
> nsinit exec date
> setsid failed. Error: Operation not permitted
> 
> Am I doing something wrong?  @vmarmol
> 
> 
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/GoogleCloudPlatform/kubernetes/pull/825/files#r16003155