NoCloud: support seed of nocloud from smbios information

This allows the user to seed NoCloud in a trivial way from qemu/libvirt,
by using a stock image and passing a single command line flag.  No custom
command line, no filesystem modification, no bootstrap disk image.

This is particularly handy now that Ec2 backend is discouraged from use
under bug 1660385.

LP: #1691772

1 files changed, 22 insertions, 0 deletions

diff --git a/doc/rtd/topics/datasources/nocloud.rst b/doc/rtd/topics/datasources/nocloud.rst
index 0159e853..665057f3 100644
--- a/doc/rtd/topics/datasources/nocloud.rst
+++ b/doc/rtd/topics/datasources/nocloud.rst
@@ -11,6 +11,28 @@ You can provide meta-data and user-data to a local vm boot via files on a
 `vfat`_ or `iso9660`_ filesystem. The filesystem volume label must be
 ``cidata``.
 
+Alternatively, you can provide meta-data via kernel command line or SMBIOS
+"serial number" option. The data must be passed in the form of a string:
+
+::
+
+  ds=nocloud[;key=val;key=val]
+
+or
+
+::
+
+  ds=nocloud-net[;key=val;key=val]
+
+e.g. you can pass this option to QEMU:
+
+::
+
+  -smbios type=1,serial=ds=nocloud-net;s=http://10.10.0.1:8000/
+
+to cause NoCloud to fetch the full meta-data from http://10.10.0.1:8000/meta-data
+after the network initialization is complete.
+
 These user-data and meta-data files are expected to be in the following format.
 
 ::