pexpect: Make standard boot logic work with quiet boot

When booting with "quiet" on the command line, the "Freeing unused
kernel" message doesn't appear.

Look also for the expected prompt, or the "login:" banner. Tested with
buildroot rootdisk, Fedora & Ubuntu.

Author: mpe

lib/pexpect_utils.py

@@ -103,19 +103,26 @@ def cmd(self, cmd):
 
 def standard_boot(p, login=False, user='root', password=None, timeout=-1):
     logging.info("Waiting for kernel to boot")
-    p.expect("Freeing unused kernel ", timeout=timeout)
+    i = p.expect([p.prompt, "login:", "Freeing unused kernel "], timeout=timeout)
+
+    if i == 0:
+        # We booted straight to a prompt, we're done
+        pass
+    elif login:
+        if i != 1:
+            logging.info("Kernel came up, waiting for login ...")
+            p.expect("login:", timeout=timeout)
 
-    if login:
-        logging.info("Kernel came up, waiting for login ...")
-        p.expect("login:", timeout=timeout)
         p.send(user)
         if password is not None:
             p.expect("Password:", timeout=timeout)
             p.send(password)
+
+        p.expect_prompt(timeout=timeout)
     else:
         logging.info("Kernel came up, waiting for prompt ...")
+        p.expect_prompt(timeout=timeout)
 
-    p.expect_prompt(timeout=timeout)
     logging.info("Booted to shell prompt")