check for existence before chmod/chown/chcon (#206)

code review feedback

azurelinuxagent/common/osutil/default.py

@@ -194,7 +194,7 @@ class DefaultOSUtil(object):
         """
         path, thumbprint, value = pubkey
         if path is None:
-            raise OSUtilError("Publich key path is None")
+            raise OSUtilError("Public key path is None")
 
         crytputil = CryptUtil(conf.get_openssl_cmd())
 
@@ -261,6 +261,9 @@ class DefaultOSUtil(object):
         Returns exit result.
         """
         if self.is_selinux_system():
+            if not os.path.exists(path):
+                logger.error("Path does not exist: {0}".format(path))
+                return 1
             return shellutil.run('chcon ' + con + ' ' + path)
 
     def conf_sshd(self, disable_password):

azurelinuxagent/common/utils/fileutil.py

@@ -91,11 +91,17 @@ def mkdir(dirpath, mode=None, owner=None):
         chowner(dirpath, owner)
 
 def chowner(path, owner):
-    owner_info = pwd.getpwnam(owner)
-    os.chown(path, owner_info[2], owner_info[3])
+    if not os.path.exists(path):
+        logger.error("Path does not exist: {0}".format(path))
+    else:
+        owner_info = pwd.getpwnam(owner)
+        os.chown(path, owner_info[2], owner_info[3])
 
 def chmod(path, mode):
-    os.chmod(path, mode)
+    if not os.path.exists(path):
+        logger.error("Path does not exist: {0}".format(path))
+    else:
+        os.chmod(path, mode)
 
 def rm_files(*args):
     for path in args:

bin/waagent2.0

@@ -228,6 +228,9 @@ class AbstractDistro(object):
         Returns exit result.
         """
         if self.isSelinuxSystem():
+            if not os.path.exists(path):
+                Error("Path does not exist: {0}".format(path))
+                return 1
             return Run('chcon ' + cn + ' ' + path)
         
     def setHostname(self,name):
@@ -2336,7 +2339,10 @@ def ChangeOwner(filepath, user):
     except:
         pass
     if p != None:
-        os.chown(filepath, p[2], p[3])
+        if not os.path.exists(filepath):
+            Error("Path does not exist: {0}".format(filepath))
+        else:
+            os.chown(filepath, p[2], p[3])
 
 def CreateDir(dirpath, user, mode):
     """