mounts: support reliably detecting and using Azure ephemeral disks

Azure's ephemeral disks are not guaranteed to be assigned the same name by
the kernel every boot. This causes problems on ~2% of Azure instances, and
can be fixed by using udev rules to give us a deterministic path to mount;
this patch introduces those udev rules and modifies the Azure data source
to use them.

Changes to a couple of config modules were also required. In some places,
they just needed to learn to dereference symlinks. In cc_mounts this
wasn't sufficient because the dereferenced device would have been put in
/etc/fstab (rather defeating the point of using the udev rules in the
first place). A fairly hefty refactor was required to separate "is this a
valid block device?" from "what shall I put in fstab?".

LP: #1411582

1 files changed, 2 insertions, 0 deletions

diff --git a/setup.py b/setup.py
index e88d9e88..5f61681b 100755
--- a/setup.py
+++ b/setup.py
@@ -84,6 +84,7 @@ INITSYS_TYPES = sorted(list(INITSYS_ROOTS.keys()))
 USR = "/usr"
 ETC = "/etc"
 USR_LIB_EXEC = "/usr/lib"
+LIB = "/lib"
 if os.uname()[0] == 'FreeBSD':
     USR = "/usr/local"
     USR_LIB_EXEC = "/usr/local/lib"
@@ -167,6 +168,7 @@ else:
             [f for f in glob('doc/examples/*') if is_f(f)]),
         (USR + '/share/doc/cloud-init/examples/seed',
             [f for f in glob('doc/examples/seed/*') if is_f(f)]),
+        (LIB + '/udev/rules.d', ['udev/66-azure-ephemeral.rules']),
     ]
     # Use a subclass for install that handles
     # adding on the right init system configuration files