Implemet docker update command

It's used for updating properties of one or more containers, we only
support resource configs for now. It can be extended in the future.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

daemon/execdriver/driver.go

@@ -91,6 +91,9 @@ type Driver interface {
 	// Stats returns resource stats for a running container
 	Stats(id string) (*ResourceStats, error)
 
+	// Update updates resource configs for a container
+	Update(c *Command) error
+
 	// SupportsHooks refers to the driver capability to exploit pre/post hook functionality
 	SupportsHooks() bool
 }

daemon/execdriver/native/driver.go

@@ -398,6 +398,26 @@ func (d *Driver) Stats(id string) (*execdriver.ResourceStats, error) {
 	}, nil
 }
 
+// Update updates configs for a container
+func (d *Driver) Update(c *execdriver.Command) error {
+	d.Lock()
+	cont := d.activeContainers[c.ID]
+	d.Unlock()
+	if cont == nil {
+		return execdriver.ErrNotRunning
+	}
+	config := cont.Config()
+	if err := execdriver.SetupCgroups(&config, c); err != nil {
+		return err
+	}
+
+	if err := cont.Set(config); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // TtyConsole implements the exec driver Terminal interface.
 type TtyConsole struct {
 	console libcontainer.Console

daemon/execdriver/windows/update.go

@@ -0,0 +1,14 @@
+// +build windows
+
+package windows
+
+import (
+	"fmt"
+
+	"github.com/docker/docker/daemon/execdriver"
+)
+
+// Update updates resource configs for a container.
+func (d *Driver) Update(c *execdriver.Command) error {
+	return fmt.Errorf("Windows: Update not implemented")
+}