add previous-instance-id and previous-datasource files to cloud/data

add 'datasource' file to instance dir

ChangeLog

@@ -1,6 +1,8 @@
 0.6.1:
  - fix bug in fixing permission on /var/log/cloud-init.log (LP: #704509)
  - improve comment strings in rsyslog file tools/21-cloudinit.conf
+ - add previous-instance-id and previous-datasource files to datadir
+ - add 'datasource' file to instance dir
 0.6.0:
  - change permissions of /var/log/cloud-init.log to accomodate
    syslog writing to it (LP: #704509)

cloudinit/__init__.py

@@ -208,7 +208,8 @@ class CloudInit:
         except OSError as e:
             if e.errno != errno.ENOENT: raise
 
-        os.symlink("./instances/%s" % self.get_instance_id(), cur_instance_link)
+        iid = self.get_instance_id()
+        os.symlink("./instances/%s" % iid, cur_instance_link)
         idir = self.get_ipath()
         dlist = []
         for d in [ "handlers", "scripts", "sem" ]:
@@ -216,6 +217,12 @@ class CloudInit:
             
         util.ensure_dirs(dlist)
 
+        ds = "%s: %s\n" % ( self.datasource.__class__, str(self.datasource) )
+        dp = self.get_cpath('datadir')
+        util.write_file("%s/%s" % (idir, 'datasource'), ds)
+        util.write_file("%s/%s" % (dp, 'previous-datasource'), ds)
+        util.write_file("%s/%s" % (dp, 'previous-instance-id'), "%s\n" % iid)
+
     def get_userdata(self):
         return(self.datasource.get_userdata())
 

doc/var-lib-cloud.txt

@@ -38,7 +38,8 @@
          boot-finished
             # this file indicates when "boot" is finished
             # it is created by the 'final_message' cloud-config
-          
+         datasource # a file containing the class and string of datasource
+
   - sem/
       scripts.once
     These are the cloud-specific semaphores.  The only thing that
@@ -52,6 +53,9 @@
   - data/
       this is a persistent data location.  cloud-init won't really
       use it, but something else (a handler or script could)
+      previous-datasource
+      previous-instance-id
+      previous-hostname
 
 to clear out the current instance's data as if to force a "new run" on reboot
 do: