add warnings for docker-only flags

pkg/kubelet/config/flags.go

@@ -17,6 +17,8 @@ limitations under the License.
 package config
 
 import (
+	"fmt"
+
 	"github.com/spf13/pflag"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
@@ -70,6 +72,8 @@ type ContainerRuntimeOptions struct {
 }
 
 func (s *ContainerRuntimeOptions) AddFlags(fs *pflag.FlagSet) {
+	dockerOnlyWarning := "This docker-specific flag only works when container-runtime is set to docker."
+
 	// General settings.
 	fs.StringVar(&s.ContainerRuntime, "container-runtime", s.ContainerRuntime, "The container runtime to use. Possible values: 'docker', 'remote', 'rkt (deprecated)'.")
 	fs.StringVar(&s.RuntimeCgroups, "runtime-cgroups", s.RuntimeCgroups, "Optional absolute name of cgroups to create and run the runtime in.")
@@ -79,15 +83,15 @@ func (s *ContainerRuntimeOptions) AddFlags(fs *pflag.FlagSet) {
 	fs.MarkHidden("experimental-dockershim")
 	fs.StringVar(&s.DockershimRootDirectory, "experimental-dockershim-root-directory", s.DockershimRootDirectory, "Path to the dockershim root directory.")
 	fs.MarkHidden("experimental-dockershim-root-directory")
-	fs.BoolVar(&s.DockerDisableSharedPID, "docker-disable-shared-pid", s.DockerDisableSharedPID, "Setting this to false causes Kubernetes to create pods using a shared process namespace for containers in a pod when running with Docker 1.13.1 or higher. A future Kubernetes release will make this configurable instead in the API.")
+	fs.BoolVar(&s.DockerDisableSharedPID, "docker-disable-shared-pid", s.DockerDisableSharedPID, fmt.Sprintf("Setting this to false causes Kubernetes to create pods using a shared process namespace for containers in a pod when running with Docker 1.13.1 or higher. A future Kubernetes release will make this configurable instead in the API. %s", dockerOnlyWarning))
 	fs.MarkDeprecated("docker-disable-shared-pid", "will be removed in a future release. This option will be replaced by PID namespace sharing that is configurable per-pod using the API. See https://features.k8s.io/495")
-	fs.StringVar(&s.PodSandboxImage, "pod-infra-container-image", s.PodSandboxImage, "The image whose network/ipc namespaces containers in each pod will use.")
-	fs.StringVar(&s.DockerEndpoint, "docker-endpoint", s.DockerEndpoint, "Use this for the docker endpoint to communicate with")
-	fs.DurationVar(&s.ImagePullProgressDeadline.Duration, "image-pull-progress-deadline", s.ImagePullProgressDeadline.Duration, "If no pulling progress is made before this deadline, the image pulling will be cancelled.")
+	fs.StringVar(&s.PodSandboxImage, "pod-infra-container-image", s.PodSandboxImage, fmt.Sprintf("The image whose network/ipc namespaces containers in each pod will use. %s", dockerOnlyWarning))
+	fs.StringVar(&s.DockerEndpoint, "docker-endpoint", s.DockerEndpoint, fmt.Sprintf("Use this for the docker endpoint to communicate with %s", dockerOnlyWarning))
+	fs.DurationVar(&s.ImagePullProgressDeadline.Duration, "image-pull-progress-deadline", s.ImagePullProgressDeadline.Duration, fmt.Sprintf("If no pulling progress is made before this deadline, the image pulling will be cancelled. %s", dockerOnlyWarning))
 
 	// Network plugin settings for Docker.
-	fs.StringVar(&s.NetworkPluginName, "network-plugin", s.NetworkPluginName, "<Warning: Alpha feature> The name of the network plugin to be invoked for various events in kubelet/pod lifecycle")
-	fs.StringVar(&s.CNIConfDir, "cni-conf-dir", s.CNIConfDir, "<Warning: Alpha feature> The full path of the directory in which to search for CNI config files. Default: /etc/cni/net.d")
-	fs.StringVar(&s.CNIBinDir, "cni-bin-dir", s.CNIBinDir, "<Warning: Alpha feature> A comma-separated list of full paths of directories in which to search for CNI plugin binaries. Default: /opt/cni/bin")
-	fs.Int32Var(&s.NetworkPluginMTU, "network-plugin-mtu", s.NetworkPluginMTU, "<Warning: Alpha feature> The MTU to be passed to the network plugin, to override the default. Set to 0 to use the default 1460 MTU.")
+	fs.StringVar(&s.NetworkPluginName, "network-plugin", s.NetworkPluginName, fmt.Sprintf("<Warning: Alpha feature> The name of the network plugin to be invoked for various events in kubelet/pod lifecycle. %s", dockerOnlyWarning))
+	fs.StringVar(&s.CNIConfDir, "cni-conf-dir", s.CNIConfDir, fmt.Sprintf("<Warning: Alpha feature> The full path of the directory in which to search for CNI config files. Default: /etc/cni/net.d. %s", dockerOnlyWarning))
+	fs.StringVar(&s.CNIBinDir, "cni-bin-dir", s.CNIBinDir, fmt.Sprintf("<Warning: Alpha feature> A comma-separated list of full paths of directories in which to search for CNI plugin binaries. Default: /opt/cni/bin. %s", dockerOnlyWarning))
+	fs.Int32Var(&s.NetworkPluginMTU, "network-plugin-mtu", s.NetworkPluginMTU, fmt.Sprintf("<Warning: Alpha feature> The MTU to be passed to the network plugin, to override the default. Set to 0 to use the default 1460 MTU. %s", dockerOnlyWarning))
 }