Merge pull request #41017 from luxas/symlink_hyperkube

Automatic merge from submit-queue (batch tested with PRs 38252, 41122, 36101, 41017, 41264)

Add alternative names for the server binaries to hyperkube

**What this PR does / why we need it**:

Right now one can't swap a server image to the hyperkube image without touching the `command` field in the yaml spec, and that's daunting and leading to extra and unnecessary logic for example in kubeadm.

This makes the hyperkube image directly swappable, so now `/usr/local/bin/kube-*` is a portable first argument (or simply `kube-*` if there's a shell).

**Special notes for your reviewer**:

**Release note**:

```release-note
Align the hyperkube image to support running binaries at /usr/local/bin/ like the other server images
```
@jessfraz @thockin @ixdy

cluster/images/hyperkube/Dockerfile

@@ -66,6 +66,8 @@ COPY cni-bin/bin /opt/cni/bin
 COPY cni-conf /etc/cni/net.d
 
 # Create symlinks for each hyperkube server
+# Also create symlinks to /usr/local/bin/ where the server image binaries live, so the hyperkube image may be 
+# used instead of gcr.io/google_containers/kube-* without any modifications.
 # TODO: replace manual symlink creation with --make-symlink command once
 # cross-building with qemu supports go binaries. See #28702
 # RUN /hyperkube --make-symlinks
@@ -76,8 +78,15 @@ RUN ln -s /hyperkube /apiserver \
  && ln -s /hyperkube /kubectl \
  && ln -s /hyperkube /kubelet \
  && ln -s /hyperkube /proxy \
- && ln -s /hyperkube /scheduler
+ && ln -s /hyperkube /scheduler \
+ && ln -s /hyperkube /usr/local/bin/kube-apiserver \
+ && ln -s /hyperkube /usr/local/bin/kube-controller-manager \
+ && ln -s /hyperkube /usr/local/bin/federation-apiserver \
+ && ln -s /hyperkube /usr/local/bin/federation-controller-manager \
+ && ln -s /hyperkube /usr/local/bin/kubectl \
+ && ln -s /hyperkube /usr/local/bin/kubelet \
+ && ln -s /hyperkube /usr/local/bin/kube-proxy \
+ && ln -s /hyperkube /usr/local/bin/kube-scheduler
 
 # Copy the hyperkube binary
 COPY hyperkube /hyperkube
-

cmd/hyperkube/hyperkube.go

@@ -55,7 +55,7 @@ func (hk *HyperKube) AddServer(s *Server) {
 // FindServer will find a specific server named name.
 func (hk *HyperKube) FindServer(name string) (*Server, error) {
 	for _, s := range hk.servers {
-		if s.Name() == name {
+		if s.Name() == name || s.AlternativeName == name {
 			return &s, nil
 		}
 	}

cmd/hyperkube/kube-apiserver.go

@@ -27,6 +27,8 @@ func NewKubeAPIServer() *Server {
 	s := options.NewServerRunOptions()
 
 	hks := Server{
+		name:            "apiserver",
+		AlternativeName: "kube-apiserver",
 		SimpleUsage:     "apiserver",
 		Long:            "The main API entrypoint and interface to the storage system.  The API server is also the focal point for all authorization decisions.",
 		Run: func(_ *Server, args []string) error {

cmd/hyperkube/kube-controller-manager.go

@@ -27,6 +27,8 @@ func NewKubeControllerManager() *Server {
 	s := options.NewCMServer()
 
 	hks := Server{
+		name:            "controller-manager",
+		AlternativeName: "kube-controller-manager",
 		SimpleUsage:     "controller-manager",
 		Long:            "A server that runs a set of active components. This includes replication controllers, service endpoints and nodes.",
 		Run: func(_ *Server, args []string) error {

cmd/hyperkube/kube-proxy.go

@@ -32,6 +32,8 @@ func NewKubeProxy() *Server {
 	config := options.NewProxyConfig()
 
 	hks := Server{
+		name:            "proxy",
+		AlternativeName: "kube-proxy",
 		SimpleUsage:     "proxy",
 		Long: `The Kubernetes proxy server is responsible for taking traffic directed at
 		services and forwarding it to the appropriate pods. It generally runs on

cmd/hyperkube/kube-scheduler.go

@@ -27,6 +27,8 @@ func NewScheduler() *Server {
 	s := options.NewSchedulerServer()
 
 	hks := Server{
+		name:            "scheduler",
+		AlternativeName: "kube-scheduler",
 		SimpleUsage:     "scheduler",
 		Long:            "Implements a Kubernetes scheduler.  This will assign pods to kubelets based on capacity and constraints.",
 		Run: func(_ *Server, _ []string) error {

cmd/hyperkube/kubelet.go

@@ -26,6 +26,7 @@ import (
 func NewKubelet() *Server {
 	s := options.NewKubeletServer()
 	hks := Server{
+		name:        "kubelet",
 		SimpleUsage: "kubelet",
 		Long: `The kubelet binary is responsible for maintaining a set of containers on a
 		particular node. It syncs data from a variety of sources including a

cmd/hyperkube/server.go

@@ -33,6 +33,7 @@ type Server struct {
 	SimpleUsage     string        // One line description of the server.
 	Long            string        // Longer free form description of the server
 	Run             serverRunFunc // Run the server.  This is not expected to return.
+	AlternativeName string
 
 	flags *pflag.FlagSet // Flags for the command (and all dependents)
 	name  string