cc_mounts may need to translate device names for xvda or virtio

[Scott Moser]

As shown in cloud-config syntax at [1], cloud-init allows the user to a name that will appear in the metadata service instead of a device name. For example, the user can specify:
  - [ ephemeral0, /mnt, auto, "defaults,noexec" ]

If the metadata service contains something like:
 'block-device-mapping': {'ami': 'sda1',
                          'ephemeral0': 'sda2',
                          'root': '/dev/sda1',
                          'swap': 'sda3'},

Then an entry in /etc/fstab will be added for 'sda2'.

There are 2 possibilities that the string 'sda2' will be wrong.
a.) on ec2, we're using a -virtual kernel, or some kernel without a patch to make xen block devices show up as 'sdX' rather than 'xvdX'. Currently our -ec2 kernels have xen block devices as sdX, but this may change.
b.) on eucalyptus, with virtio as root device and/or ebs. In this case, the metadata service will still likely have 'sdX' but the kernel devices would be named vdX.

In either case, some trickery will have to be done to decide to rename.

Really, this is just a general problem with the metadata service provided by the hypervisor believing it knows certain things about the OS that is running in it.

--
[1] http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/annotate/head%3A/doc/examples/cloud-config.txt

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: eucalyptus-nc 2.0~bzr1211-0ubuntu1
ProcVersionSignature: User Name 2.6.32-305.9-ec2 2.6.32.11+drm33.2
Uname: Linux 2.6.32-305-ec2 i686
Architecture: i386
Date: Thu Jul 29 03:06:03 2010
Ec2AMI: ami-e930db80
Ec2AMIManifest: ubuntu-images-testing-us/ubuntu-maverick-daily-i386-server-20100727.manifest.xml
Ec2AvailabilityZone: us-east-1b
Ec2InstanceType: m1.small
Ec2Kernel: aki-407d9529
Ec2Ramdisk: unavailable
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: eucalyptus

[Scott Moser (smoser)]

verified with 2.0~bzr1211-0ubuntu1 that with virtio root, you get:
 'block-device-mapping': {'emi': 'sda1',
                          'ephemeral': 'sda2',
                          'ephemeral0': 'sda2',
                          'root': '/dev/sda1',
                          'swap': 'sda3'},
while
$ cat /proc/partitions
major minor #blocks name

 252 0 2132992 vda
 252 1 1441792 vda1
 252 2 94000 vda2
 252 3 597167 vda3

[Scott Moser (smoser)]

I've verified also that with virtio root, /mnt (ephemeral0) is not mounted.

[Scott Moser (smoser)]

This is fixed in cloud-init 0.5.14

[Pete Crossley (peterc)]

I merged this change to DataSourceEc2.py to my local repo for lucid could we get this applied to lucid updates as well?

[Scott Moser (smoser)]

this is confirmed on lucid if you boot a maverick or newer kernel with it.

[Scott Moser (smoser)]

just for easy reference, the fix was applied to trunk at revno 237 http://paste.ubuntu.com/1517992/

[Rolf Leggewie (r0lf)]

lucid has seen the end of its life and is no longer receiving any updates. Marking the lucid task for this ticket as "Won't Fix".