Skip etcd related preflight checks and reset actions for external etcd

We should not assume ownership of etcd when external etcd endpoints were
set.

Fixes: https://github.com/kubernetes/kubeadm/issues/69

cmd/kubeadm/app/cmd/reset.go

@@ -131,9 +131,16 @@ func (r *Reset) Run(out io.Writer) error {
 	// Don't check for errors here, since umount will return a non-zero exit code if there is no directories to umount
 	exec.Command("sh", "-c", "cat /proc/mounts | awk '{print $2}' | grep '/var/lib/kubelet' | xargs umount").Run()
 
+	dirsToClean := []string{"/var/lib/kubelet"}
+
+	// Only clear etcd data when the etcd manifest is found. In case it is not found, we must assume that the user
+	// provided external etcd endpoints. In that case, it is his own responsibility to reset etcd
+	if _, err := os.Stat("/etc/kubernetes/manifests/etcd.json"); os.IsNotExist(err) {
+		dirsToClean = append(dirsToClean, "/var/lib/etcd")
+	}
+
 	resetConfigDir("/etc/kubernetes/")
 
-	dirsToClean := []string{"/var/lib/kubelet", "/var/lib/etcd"}
 	fmt.Printf("Deleting contents of stateful directories: %v\n", dirsToClean)
 	for _, dir := range dirsToClean {
 		cleanDir(dir)

cmd/kubeadm/app/preflight/checks.go

@@ -221,7 +221,6 @@ func RunInitMasterChecks(cfg *kubeadmapi.MasterConfiguration) error {
 		ServiceCheck{Service: "kubelet"},
 		ServiceCheck{Service: "docker"},
 		PortOpenCheck{port: int(cfg.API.BindPort)},
-		PortOpenCheck{port: 2379},
 		PortOpenCheck{port: 8080},
 		PortOpenCheck{port: int(cfg.Discovery.BindPort)},
 		PortOpenCheck{port: 10250},
@@ -230,7 +229,6 @@ func RunInitMasterChecks(cfg *kubeadmapi.MasterConfiguration) error {
 		HttpProxyCheck{Proto: "https", Host: cfg.API.AdvertiseAddresses[0], Port: int(cfg.API.BindPort)},
 		DirAvailableCheck{Path: "/etc/kubernetes/manifests"},
 		DirAvailableCheck{Path: "/etc/kubernetes/pki"},
-		DirAvailableCheck{Path: "/var/lib/etcd"},
 		DirAvailableCheck{Path: "/var/lib/kubelet"},
 		FileAvailableCheck{Path: "/etc/kubernetes/admin.conf"},
 		FileAvailableCheck{Path: "/etc/kubernetes/kubelet.conf"},
@@ -245,6 +243,14 @@ func RunInitMasterChecks(cfg *kubeadmapi.MasterConfiguration) error {
 		InPathCheck{executable: "touch", mandatory: false},
 	}
 
+	if len(cfg.Etcd.Endpoints) == 0 {
+		// Only do etcd related checks when no external endpoints were specified
+		checks = append(checks,
+			PortOpenCheck{port: 2379},
+			DirAvailableCheck{Path: "/var/lib/etcd"},
+		)
+	}
+
 	return runChecks(checks, os.Stderr)
 }