fix who -b issue on Ubuntu 14.04

who -b doesn't return value in first boot on Ubuntu 14.04. Use uptime -s
to get boot time. uptime -s doesn't exists on some centos version, so
it's not default command.

lisa/tools/__init__.py

@@ -10,6 +10,7 @@ from .modinfo import Modinfo
 from .ntttcp import Ntttcp
 from .reboot import Reboot
 from .uname import Uname
+from .uptime import Uptime
 from .who import Who
 
 __all__ = [
@@ -25,5 +26,6 @@ __all__ = [
     "Ntttcp",
     "Reboot",
     "Uname",
+    "Uptime",
     "Who",
 ]

lisa/tools/reboot.py

@@ -8,6 +8,7 @@ from lisa.util.perf_timer import create_timer
 from lisa.util.process import ExecutableResult
 
 from .date import Date
+from .uptime import Uptime
 from .who import Who
 
 
@@ -26,7 +27,14 @@ class Reboot(Tool):
     def reboot(self) -> None:
         who = self.node.tools[Who]
         timer = create_timer()
+
+        # who -b doesn't return correct content in Ubuntu 14.04, but uptime works.
+        # uptime has no -s parameter in some distros, so not use is as default.
+        try:
             last_boot_time = who.last_boot()
+        except Exception:
+            uptime = self.node.tools[Uptime]
+            last_boot_time = uptime.since_time()
         current_boot_time = last_boot_time
 
         # who -b returns time without seconds.

lisa/tools/uptime.py

@@ -0,0 +1,23 @@
+from datetime import datetime
+
+from dateutil.parser import parser
+
+from lisa.executable import Tool
+from lisa.util import LisaException
+
+
+class Uptime(Tool):
+    @property
+    def command(self) -> str:
+        return "uptime"
+
+    def _check_exists(self) -> bool:
+        return True
+
+    def since_time(self, no_error_log: bool = True) -> datetime:
+        command_result = self.run("-s", no_error_log=no_error_log)
+        if command_result.exit_code != 0:
+            raise LisaException(
+                f"get unexpected non-zero exit code {command_result.exit_code}"
+            )
+        return parser().parse(command_result.stdout)