Initial hotplug support (#936)

Adds a udev script which will invoke a hotplug hook script on all net
add events. The script will write some udev arguments to a systemd FIFO
socket (to ensure we have only instance of cloud-init running at a
time), which is then read by a new service that calls a new 'cloud-init
devel hotplug-hook' command to handle the new event.

This hotplug-hook command will:
- Fetch the pickled datsource
- Verify that the hotplug event is supported/enabled
- Update the metadata for the datasource
- Ensure the hotplugged device exists within the datasource
- Apply the config change on the datasource metadata
- Bring up the new interface (or apply global network configuration)
- Save the updated metadata back to the pickle cache

Also scattered in some unrelated typing where helpful

1 files changed, 3 insertions, 0 deletions

diff --git a/cloudinit/cmd/devel/parser.py b/cloudinit/cmd/devel/parser.py
index 1a3c46a4..be304630 100644
--- a/cloudinit/cmd/devel/parser.py
+++ b/cloudinit/cmd/devel/parser.py
@@ -7,6 +7,7 @@
 import argparse
 from cloudinit.config import schema
 
+from . import hotplug_hook
 from . import net_convert
 from . import render
 from . import make_mime
@@ -21,6 +22,8 @@ def get_parser(parser=None):
     subparsers.required = True
 
     subcmds = [
+        (hotplug_hook.NAME, hotplug_hook.__doc__,
+         hotplug_hook.get_parser, hotplug_hook.handle_args),
         ('schema', 'Validate cloud-config files for document schema',
          schema.get_parser, schema.handle_schema_args),
         (net_convert.NAME, net_convert.__doc__,