Merge pull request #17704 from LK4D4/default_cgroupfs

Use fs cgroups by default

daemon/execdriver/native/driver.go

@@ -74,9 +74,6 @@ func NewDriver(root, initPath string, options []string) (*Driver, error) {
 	// this makes sure there are no breaking changes to people
 	// who upgrade from versions without native.cgroupdriver opt
 	cgm := libcontainer.Cgroupfs
-	if systemd.UseSystemd() {
-		cgm = libcontainer.SystemdCgroups
-	}
 
 	// parse the options
 	for _, option := range options {

docs/reference/commandline/daemon.md

@@ -446,11 +446,11 @@ single `native.cgroupdriver` option is available.
 
 The `native.cgroupdriver` option specifies the management of the container's
 cgroups. You can specify `cgroupfs` or `systemd`. If you specify `systemd` and
-it is not available, the system uses `cgroupfs`. By default, if no option is
-specified, the execdriver first tries `systemd` and falls back to `cgroupfs`.
-This example sets the execdriver to `cgroupfs`:
+it is not available, the system uses `cgroupfs`. If you omit the
+`native.cgroupdriver` option,` cgroupfs` is used.
+This example sets the `cgroupdriver` to `systemd`:
 
-    $ sudo docker daemon --exec-opt native.cgroupdriver=cgroupfs
+    $ sudo docker daemon --exec-opt native.cgroupdriver=systemd
 
 Setting this option applies to all containers the daemon launches.