[CentOS] CentOS 6.x, kernel-2.6.32-220.7.1, EC2 and drive enumeration

Tue Apr 17 11:53:15 UTC 2012
Steph Gosling <steph at chuci.org>

On Tue, 17 Apr 2012 12:35:07 +0100
Karanbir Singh <mail-lists at karan.org> wrote:

> hi,
> Please dont toppost, trim your reply and keep context in your replies.

Apologies (mail sent before coffee this morning!)

> On 04/17/2012 08:04 AM, Steph Gosling wrote:
> > them as 'xvdN' but N in this case is 'e', not 'a', 'f', not 'b' and so
> > on.
> And labels dont help here ?

Labels do help for the root device but not for ephemeral devices in
EC2:- with an EC2 instance you'll know the label or UUID of the root
device but ephemeral devices are created at startup time. This makes
getting mountpoints right hard if you're programmatically starting
instances difficult. 

There's also a 'mapping' between what the EC2 APIs return as the root
device (helpfully still referred to via the old SCSI names), again
which makes programmatic operations break: expecting something to
be /dev/sda1 in EC2 that was /dev/xvda1 in the instance but magically
now is /dev/xvde1.

Anyway as I say it's definitely a problem with upstream so we'll just
wait and see. Just explaining this here so that the search engines get
it and it'll hopefully help someone else with the same problem in the



Steph Gosling <steph at chuci.org>