kubelet: change image-gc-threshold below docker dm.min_free_space

cmd/kubelet/app/options/options.go

@@ -173,7 +173,7 @@ func (s *KubeletServer) AddFlags(fs *pflag.FlagSet) {
 	bindableNodeLabels := utilflag.ConfigurationMap(s.NodeLabels)
 	fs.Var(&bindableNodeLabels, "node-labels", "<Warning: Alpha feature> Labels to add when registering the node in the cluster.  Labels must be key=value pairs separated by ','.")
 	fs.DurationVar(&s.ImageMinimumGCAge.Duration, "minimum-image-ttl-duration", s.ImageMinimumGCAge.Duration, "Minimum age for an unused image before it is garbage collected.  Examples: '300ms', '10s' or '2h45m'. Default: '2m'")
-	fs.Int32Var(&s.ImageGCHighThresholdPercent, "image-gc-high-threshold", s.ImageGCHighThresholdPercent, "The percent of disk usage after which image garbage collection is always run. Default: 90%")
+	fs.Int32Var(&s.ImageGCHighThresholdPercent, "image-gc-high-threshold", s.ImageGCHighThresholdPercent, "The percent of disk usage after which image garbage collection is always run. Default: 85%")
 	fs.Int32Var(&s.ImageGCLowThresholdPercent, "image-gc-low-threshold", s.ImageGCLowThresholdPercent, "The percent of disk usage before which image garbage collection is never run. Lowest disk usage to garbage collect to. Default: 80%")
 	fs.Int32Var(&s.LowDiskSpaceThresholdMB, "low-diskspace-threshold-mb", s.LowDiskSpaceThresholdMB, "The absolute free disk space, in MB, to maintain. When disk space falls below this threshold, new pods would be rejected. Default: 256")
 	fs.DurationVar(&s.VolumeStatsAggPeriod.Duration, "volume-stats-agg-period", s.VolumeStatsAggPeriod.Duration, "Specifies interval for kubelet to calculate and cache the volume disk usage for all pods and volumes.  To disable volume calculations, set to 0.  Default: '1m'")

pkg/apis/componentconfig/v1alpha1/defaults.go

@@ -266,7 +266,8 @@ func SetDefaults_KubeletConfiguration(obj *KubeletConfiguration) {
 		obj.ImageMinimumGCAge = metav1.Duration{Duration: 2 * time.Minute}
 	}
 	if obj.ImageGCHighThresholdPercent == nil {
-		temp := int32(90)
+		// default is below docker's default dm.min_free_space of 90%
+		temp := int32(85)
 		obj.ImageGCHighThresholdPercent = &temp
 	}
 	if obj.ImageGCLowThresholdPercent == nil {