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List:       xen-users
Subject:    Re: [Xen-users] Guest O/S Questions
From:       "Karsten M. Self" <karsten () xensource ! com>
Date:       2005-08-30 22:50:19
Message-ID: 4314E2AB.2090207 () xensource ! com
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Anthony Liguori wrote:

> Marcus Brown wrote:
>
>>> You're right.  fdisk (and AFAIK, modern partitioning tools) prefer to
>>> start partitions on the first cylinder boundary.  The assumption 
>>> here is
>>> that each cylinder contains 63 sectors.
>>>   
>>
>>
>> OK, but why skip this cylinder?
>> If you are creating an image with multiple partitions won't you need to
>> keep the partition table intact?
>>  
>>
> Ok, let's back track a little.  The dd command I suggested is only 
> useful for extracting the first partition from a partitioned disk 
> image assuming that the first partition occupies all of the remaining 
> disk space and starts on the 63rd sector.

... *and* the goal is to end up with a filesystem image, *not* a 
partitioned file image.

Eg:  what's extracted is similar to what you'd get with:

   dd if=/dev/zero bs=1M seek=100 count=0 of=fs_image
   mke2fs -F fs_image
   mkdir mp
   mount -o loop -t ext2 fs_image mp

More traditional use of filesystem image files has been for files 
_without_ partition tables.

...or, to answer your question:  if you're extracting individual 
filesystems to their own file, you _don't_ need to keep the partition 
table intact.

-- 
Karsten M. Self <karsten@xensource.com>
XenSource, Inc.
2300 Geng Road #250                                +1 650.798.5900 x259
Palo Alto, CA 94303                                +1 650.493.1579 fax


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