Merge lp:~smoser/maas-images/trunk.ppa-proposed-doc into lp:maas-images

[Scott Moser]

README: add info about building with ppa or proposed.

This just documents functionality that was previously exposed.
The usage of PPA is specifically nice for testing things.

[Lee Trager (ltrager)]

LGTM thanks for adding some documentation!

review: Approve

[lp:~smoser/maas-images/trunk.ppa-proposed-doc]

382. By Scott Moser on 2017-10-06

minor updates

=== modified file 'README'
--- README	2016-01-25 15:52:31 +0000
+++ README	2017-10-06 20:42:39 +0000
@@ -67,6 +67,40 @@
 It will produce output that looks much like the final output, but
 runs in seconds rather than minutes.
 
+=== Enabling Proposed ===
+For development and test purposes using Ubuntu proposed or PPA can
+be very useful.
+
+You can enable the proposed archive by simply editing the config
+file conf/meph-v3.yaml and specifying '--conf=conf/meph-v3.yaml'.
+
+    enable_proposed: True
+
+Alternatively, you can simply pass '--proposed' to 'meph2-build' or
+to 'meph2-cloudimg-sync'.
+
+=== Adding PPAs ===
+You can build images with any number of PPAs added and additional
+packages installed into the image through the environment variables
+M2E_ADD_REPOS and M2E_ADD_PACKAGES which are read by
+maas-cloudimg2ephemeral.
+
+M2E_ADD_REPOS is a space-delimited list of repositories to pass
+to 'add-apt-repository'.  M2E_ADD_PACKAGES is a space-delimited
+list of packages that will be installed into the image, and will
+thus affect both the image and the initramfs produced from it.
+
+For example:
+
+    $ rel=xenial ; arch=amd64
+    $ burl=http://cloud-images.ubuntu.com/
+    $ file=$rel-server-cloudimg-amd64.squashfs
+    $ wget $burl/$rel/current/$rel-server-cloudimg-amd64.squashfs -O "$file"
+
+    $ export M2E_ADD_REPOS=ppa:smoser/lp1711760
+    $ meph2-build --config=conf/meph-v3.yaml \
+        $arch $rel $(date +"%Y%m%d") $file $rel-output.d/
+
 == streams management ==
 Building as above will create out.d that has *metadata* describing
 everything that is in the source stream and also the things that were