diff --git a/cmd/containerboot/main.go b/cmd/containerboot/main.go
index 8e9ff7185..6b50b4654 100644
--- a/cmd/containerboot/main.go
+++ b/cmd/containerboot/main.go
@@ -4,13 +4,13 @@
 
 //go:build linux
 
-// The containerboot binary is a wrapper for starting tailscaled in a
-// container. It handles reading the desired mode of operation out of
-// environment variables, bringing up and authenticating Tailscale,
-// and any other kubernetes-specific side jobs.
+// The containerboot binary is a wrapper for starting tailscaled in a container.
+// It handles reading the desired mode of operation out of environment
+// variables, bringing up and authenticating Tailscale, and any other
+// kubernetes-specific side jobs.
 //
-// As with most container things, configuration is passed through
-// environment variables. All configuration is optional.
+// As with most container things, configuration is passed through environment
+// variables. All configuration is optional.
 //
 //   - TS_AUTH_KEY: the authkey to use for login.
 //   - TS_ROUTES: subnet routes to advertise.
@@ -37,9 +37,13 @@
 //     compatibility), forcibly log in every time the
 //     container starts.
 //
-// When running on Kubernetes, TS_KUBE_SECRET takes precedence over
-// TS_STATE_DIR. Additionally, if TS_AUTH_KEY is not provided and the
-// TS_KUBE_SECRET contains an "authkey" field, that key is used.
+// When running on Kubernetes, containerboot defaults to storing state in the
+// "tailscale" kube secret. To store state on local disk instead, set
+// TS_KUBE_SECRET="" and TS_STATE_DIR=/path/to/storage/dir. The state dir should
+// be persistent storage.
+//
+// Additionally, if TS_AUTH_KEY is not set and the TS_KUBE_SECRET contains an
+// "authkey" field, that key is used as the tailscale authkey.
 package main
 
 import (
@@ -538,7 +542,7 @@ type settings struct {
 // defaultEnv returns the value of the given envvar name, or defVal if
 // unset.
 func defaultEnv(name, defVal string) string {
-	if v := os.Getenv(name); v != "" {
+	if v, ok := os.LookupEnv(name); ok {
 		return v
 	}
 	return defVal
diff --git a/cmd/containerboot/main_test.go b/cmd/containerboot/main_test.go
index 94adf8b2e..c12269f84 100644
--- a/cmd/containerboot/main_test.go
+++ b/cmd/containerboot/main_test.go
@@ -346,6 +346,31 @@ func TestContainerBoot(t *testing.T) {
 				},
 			},
 		},
+		{
+			Name: "kube_disk_storage",
+			Env: map[string]string{
+				"KUBERNETES_SERVICE_HOST":       kube.Host,
+				"KUBERNETES_SERVICE_PORT_HTTPS": kube.Port,
+				// Explicitly set to an empty value, to override the default of "tailscale".
+				"TS_KUBE_SECRET": "",
+				"TS_STATE_DIR":   filepath.Join(d, "tmp"),
+				"TS_AUTH_KEY":    "tskey-key",
+			},
+			KubeSecret: map[string]string{},
+			Phases: []phase{
+				{
+					WantCmds: []string{
+						"/usr/bin/tailscaled --socket=/tmp/tailscaled.sock --statedir=/tmp --tun=userspace-networking",
+						"/usr/bin/tailscale --socket=/tmp/tailscaled.sock up --accept-dns=false --authkey=tskey-key",
+					},
+					WantKubeSecret: map[string]string{},
+				},
+				{
+					Notify:         runningNotify,
+					WantKubeSecret: map[string]string{},
+				},
+			},
+		},
 		{
 			Name: "kube_storage_no_patch",
 			Env: map[string]string{