Print timestamp during kerf exec

Signed-off-by: Cong Wang <cwang@multikernel.io>

Author: congwang-mk

src/kerf/exec/main.py

@@ -20,6 +20,8 @@
 import os
 import platform
 import sys
+import time
+from datetime import datetime, timezone
 from pathlib import Path
 from typing import Optional
 
@@ -211,7 +213,10 @@ def exec_cmd(name: Optional[str], id: Optional[int], attach_console: bool, verbo
             click.echo(f"✓ Kernel image found for instance '{instance_name}'")
             click.echo(f"Instance ID to boot: {instance_id}")
             click.echo(f"Using reboot syscall with command: 0x{LINUX_REBOOT_CMD_MULTIKERNEL:x}")
-            click.echo("Calling reboot syscall...")
+            now = datetime.now(timezone.utc)
+            epoch_time = time.time()
+            millis = int((epoch_time % 1) * 1000)
+            click.echo(f"Calling reboot syscall at {now.strftime('%Y-%m-%d %H:%M:%S')}.{millis:03d} UTC")
         else:
             click.echo(f"Booting instance '{instance_name}' (ID: {instance_id})...")