@@ -39,8 +39,10 @@ type nopLog struct{}

 func (nopLog) Logf(string, ...interface{}) {}

-const defaultDockerdBinary = "dockerd"

-const containerdSocket = "/var/run/docker/containerd/containerd.sock"

+const (

+	defaultDockerdBinary    = "dockerd"

+	defaultContainerdSocket = "/var/run/docker/containerd/containerd.sock"

+)

 var errDaemonNotStarted = errors.New("daemon not started")

@@ -75,6 +77,7 @@ type Daemon struct {

 	log                        LogT

 	pidFile                    string

 	args                       []string

+	containerdSocket           string

 	// swarm related field

 	swarmListenAddr string

@@ -120,11 +123,12 @@ func NewDaemon(workingDir string, ops ...Option) (*Daemon, error) {

 		storageDriver: storageDriver,

 		userlandProxy: userlandProxy,

 		// dxr stands for docker-execroot (shortened for avoiding unix(7) path length limitation)

-		execRoot:        filepath.Join(os.TempDir(), "dxr", id),

-		dockerdBinary:   defaultDockerdBinary,

-		swarmListenAddr: defaultSwarmListenAddr,

-		SwarmPort:       DefaultSwarmPort,

-		log:             nopLog{},

+		execRoot:         filepath.Join(os.TempDir(), "dxr", id),

+		dockerdBinary:    defaultDockerdBinary,

+		swarmListenAddr:  defaultSwarmListenAddr,

+		SwarmPort:        DefaultSwarmPort,

+		log:              nopLog{},

+		containerdSocket: defaultContainerdSocket,

 	}

 	for _, op := range ops {

@@ -252,17 +256,20 @@ func (d *Daemon) StartWithLogFile(out *os.File, providedArgs ...string) error {

 		d.pidFile = filepath.Join(d.Folder, "docker.pid")

 	}

-	d.args = append(d.GlobalFlags,

-		"--containerd", containerdSocket,

-		"--data-root", d.Root,

+	d.args = append(d.GlobalFlags, "--data-root", d.Root)

+	if d.containerdSocket != "" {

+		d.args = append(d.args, "--containerd", d.containerdSocket)

+	}

+	d.args = append(d.args,

 		"--exec-root", d.execRoot,

 		"--pidfile", d.pidFile,

 		fmt.Sprintf("--userland-proxy=%t", d.userlandProxy),

 		"--containerd-namespace", d.id,

 		"--containerd-plugins-namespace", d.id+"p",

 	)

+

 	if d.defaultCgroupNamespaceMode != "" {

-		d.args = append(d.args, []string{"--default-cgroupns-mode", d.defaultCgroupNamespaceMode}...)

+		d.args = append(d.args, "--default-cgroupns-mode", d.defaultCgroupNamespaceMode)

 	}

 	if d.experimental {

 		d.args = append(d.args, "--experimental")

@@ -271,10 +278,10 @@ func (d *Daemon) StartWithLogFile(out *os.File, providedArgs ...string) error {

 		d.args = append(d.args, "--init")

 	}

 	if !(d.UseDefaultHost || d.UseDefaultTLSHost) {

-		d.args = append(d.args, []string{"--host", d.Sock()}...)

+		d.args = append(d.args, "--host", d.Sock())

 	}

 	if root := os.Getenv("DOCKER_REMAP_ROOT"); root != "" {

-		d.args = append(d.args, []string{"--userns-remap", root}...)

+		d.args = append(d.args, "--userns-remap", root)

 	}

 	// If we don't explicitly set the log-level or debug flag(-D) then

@@ -7,6 +7,16 @@ import (

 // Option is used to configure a daemon.

 type Option func(*Daemon)

+// WithContainerdSocket sets the --containerd option on the daemon.

+// Use an empty string to remove the option.

+//

+// If unset the --containerd option will be used with a default value.

+func WithContainerdSocket(socket string) Option {

+	return func(d *Daemon) {

+		d.containerdSocket = socket

+	}

+}

+

 // WithDefaultCgroupNamespaceMode sets the default cgroup namespace mode for the daemon

 func WithDefaultCgroupNamespaceMode(mode string) Option {

 	return func(d *Daemon) {