sd devices on FC14 AMI not valid?

Brian LaMere brian at
Thu Feb 10 02:28:37 UTC 2011

replace "sd" with "xvd" and you'll be set.  It's not a "*s*csi *d*isk" but
instead a "*x*en *v*irtual (block) *d*evice"

On older AKIs, sometimes one would see drives presented to the OS as
/dev/sd* still, but it seems like since pvgrub this is no longer the case.
 It's more "honest" this way regardless; the kernel is seeing it (or at
least, presenting it) more accurately for what it is.  It never should have
listed those drives as /dev/sd*

So...point's not supposed to be /dev/sd* - just like it wasn't
/dev/sd* when you used old IDE drives (those were /dev/hd*).  Almost all
kernels have built-in support for IDE and SCSI, but not for Xen; that's
loaded as a module, instead.  If you do an "lsmod" you should see a loaded
module named xen_blkfront - note also that it has a "used by" value that is
the same as the number of (valid...) /dev/xvd* block devices.

See for
info about that module...

Does that answer the question?  Disregard what Amazon says you should see
the device reporting as - it should be xvd*, not sd*.  It's not using the
scsi driver.


On Wed, Feb 9, 2011 at 5:49 PM, David HM Spector <spector at>wrote:

> I am trying to get an attached EBS volume to mount on a customized (ots of
> php and rails packages) version of the FC14 AMI.
> It seems the sd devices aren't made by default; but even once they're made,
> mount refuses to mount the volume
> saying " /dev/sdf is not a valid block device"   Its a an ext3 filesystem
> so nothing novel there.
> Everything works fine on my older instances with the same scripts; I can
> get he EBS volume to attach to the instance (I have
> some custom ruby scripts that work at startup to attach vol ids passed as
> user data) and the perms/maj/min device numbers
> look OK too (as one would expect from MAKEDEV).
>  Anything obvious I am missing?
> tnx,
>   David
> ----------------------------------------------------------------------------------------------
>                                           David HM Spector
> spector at zeitgeist dot com
>                                                     ~ ~ ~
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