Warn user when host is using cgroup v1

Author: ThankaBharathi

pkg/drivers/kic/oci/cgroups_linux.go

@@ -80,3 +80,21 @@ func hasMemorySwapCgroup() bool {
 	}
 	return true
 }
+
+// IsCgroupV2 returns true if the host is using cgroup v2
+func IsCgroupV2() bool {
+	_, err := os.Stat("/sys/fs/cgroup/cgroup.controllers")
+	return err == nil
+}
+
+// WarnIfCgroupV1 prints a warning if host is using cgroup v1
+func WarnIfCgroupV1() {
+	if !IsCgroupV2() {
+		klog.Warning(
+			"Host system is using cgroup v1. " +
+				"Minikube will not enable cgroup v2. " +
+				"Some features may not work as expected.",
+		)
+	}
+}
+

pkg/drivers/kic/oci/cgroups_other.go

@@ -25,3 +25,8 @@ func HasMemoryCgroup() bool {
 func hasMemorySwapCgroup() bool {
 	return true
 }
+
+// WarnIfCgroupV1 is a no-op on non-Linux systems
+func WarnIfCgroupV1() {
+	// no-op
+}

pkg/drivers/kic/oci/oci.go

@@ -159,6 +159,10 @@ func CreateContainerNode(p CreateParams) error { //nolint to suppress cyclomatic
 			return errors.Wrap(err, "daemon info")
 		}
 	}
+	if runtime.GOOS == "linux" {
+		WarnIfCgroupV1()
+	}
+
 
 	runArgs := []string{
 		"-d", // run the container detached