Allow a url to cloud-config data to be specified on kernel config line

In order to allow an ephemeral, or otherwise pristine image to
receive some configuration, cloud-init will read a url directed by
the kernel command line and proceed as if its data had previously existed.

For more information, see doc/kernel-cmdline.txt

3 files changed, 46 insertions, 0 deletions

diff --git a/cloudinit/DataSourceNoCloud.py b/cloudinit/DataSourceNoCloud.py
index 62ecc088..e8c56b8f 100644
--- a/cloudinit/DataSourceNoCloud.py
+++ b/cloudinit/DataSourceNoCloud.py
@@ -67,6 +67,13 @@ class DataSourceNoCloud(DataSource.DataSource):
             found.append(self.seeddir)
             log.debug("using seeded cache data in %s" % self.seeddir)
 
+        # if the datasource config had a 'seedfrom' entry, then that takes
+        # precedence over a 'seedfrom' that was found in a filesystem
+        # but not over external medi
+        if 'seedfrom' in self.ds_cfg and self.ds_cfg['seedfrom']:
+            found.append("ds_config")
+            md["seedfrom"] = self.ds_cfg['seedfrom']
+
         fslist = util.find_devs_with("TYPE=vfat")
         fslist.extend(util.find_devs_with("TYPE=iso9660"))
 
diff --git a/cloudinit/__init__.py b/cloudinit/__init__.py
index 6d276d84..85c6fd1b 100644
--- a/cloudinit/__init__.py
+++ b/cloudinit/__init__.py
@@ -137,7 +137,9 @@ class CloudInit:
 
         if ds_deps != None:
             self.ds_deps = ds_deps
+
         self.sysconfig = sysconfig
+
         self.cfg = self.read_cfg()
 
     def read_cfg(self):
@@ -639,3 +641,27 @@ class InternalPartHandler:
 
     def handle_part(self, data, ctype, filename, payload, frequency):
         return(self.handler(data, ctype, filename, payload, frequency))
+
+
+def get_cmdline_url(names=('cloud-config-url', 'url'),
+                    starts="#cloud-config", cmdline=None):
+
+    if cmdline == None:
+        cmdline = util.get_cmdline()
+
+    data = util.keyval_str_to_dict(cmdline)
+    url = None
+    key = None
+    for key in names:
+        if key in data:
+            url = data[key]
+            break
+    if url == None:
+        return (None, None, None)
+
+    contents = util.readurl(url)
+
+    if contents.startswith(starts):
+        return (key, url, contents)
+
+    return (key, url, None)
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 9133426c..47397418 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -840,3 +840,16 @@ def wait_for_url(urls, max_wait=None, timeout=None,
         time.sleep(sleeptime)
 
     return False
+
+
+def keyval_str_to_dict(kvstring):
+    ret = {}
+    for tok in kvstring.split():
+        try:
+            (key, val) = tok.split("=", 1)
+        except ValueError:
+            key = tok
+            val = True
+        ret[key] = val
+
+    return(ret)