diff --git a/core/src/main/java/hudson/cli/SessionIdCommand.java b/core/src/main/java/hudson/cli/SessionIdCommand.java
new file mode 100644
index 0000000000000000000000000000000000000000..5a38f489228d42435a8c2358ca28e54c36f5d100
--- /dev/null
+++ b/core/src/main/java/hudson/cli/SessionIdCommand.java
@@ -0,0 +1,24 @@
+package hudson.cli;
+
+import hudson.Extension;
+import jenkins.model.Jenkins;
+
+/**
+ * Prints the current session ID number (that changes for every run)
+ * to allow clients to reliably wait for a restart.
+ *
+ * @author Kohsuke Kawaguchi
+ */
+@Extension
+public class SessionIdCommand extends CLICommand {
+    @Override
+    public String getShortDescription() {
+        return "Outputs the session ID, which changes every time Jenkins restarts";
+    }
+
+    protected int run() {
+        stdout.println(Jenkins.SESSION_HASH);
+        return 0;
+    }
+}
+