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

3 files changed, 37 insertions, 0 deletions

diff --git a/cloudinit/sources/DataSourceNoCloud.py b/cloudinit/sources/DataSourceNoCloud.py
index c68f6b8c..e641244d 100644
--- a/cloudinit/sources/DataSourceNoCloud.py
+++ b/cloudinit/sources/DataSourceNoCloud.py
@@ -43,6 +43,18 @@ class DataSourceNoCloud(sources.DataSource):
                   'network-config': None}
 
         try:
+            # Parse the system serial label from dmi. If not empty, try parsing
+            # like the commandline
+            md = {}
+            serial = util.read_dmi_data('system-serial-number')
+            if serial and load_cmdline_data(md, serial):
+                found.append("dmi")
+                mydata = _merge_new_seed(mydata, {'meta-data': md})
+        except Exception:
+            util.logexc(LOG, "Unable to parse dmi data")
+            return False
+
+        try:
             # Parse the kernel command line, getting data passed in
             md = {}
             if load_cmdline_data(md):
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.
 
 ::
diff --git a/tools/ds-identify b/tools/ds-identify
index 546e0f59..7c8b144b 100755
--- a/tools/ds-identify
+++ b/tools/ds-identify
@@ -555,6 +555,9 @@ dscheck_NoCloud() {
     case " ${DI_KERNEL_CMDLINE} " in
         *\ ds=nocloud*) return ${DS_FOUND};;
     esac
+    case " ${DI_DMI_PRODUCT_SERIAL} " in
+        *\ ds=nocloud*) return ${DS_FOUND};;
+    esac
     for d in nocloud nocloud-net; do
         check_seed_dir "$d" meta-data user-data && return ${DS_FOUND}
     done