Hi,
I
tried with rhel5.1 to create a guest using the following config:
disk=[
'file:/opt/img-store/shared-disk,hdb,r',
'file:/var/lib/xen/images/rhel5-1/disk0,hda,w', ]
where
shared-disk is used as read-only and a separate disk0 is used to capture
the user defined guest changes as RW.. Note, shared-disk is pre-existing image meant
to share among the guests..
but
seems, all the changes made in the new guest is still writing on the read-only shared-disk,
instead disk0.
Even
if I change chmod 400 of shared-disk file, still it writes there..
I
was hoping to capture the delta changes with disk0, per guest basis to serve my
purpose..
Kindly
guide as required for the same ..
-
regards
Pallab
-----Original
Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Simon Hobson
Sent: Friday, April 17, 2009 3:14 PM
To: Xen-users@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] unionfs with xen
Pallab Chakrabarty
wrote:
>>Are
you trying to have a common filesystem image
>>shared
by many DomUs, and use unionfs to allow
>>each
DomU to have it's own modified version ?
>YES
>
>kindly
guide me..
I
don't know - not something I've ever worked with.
A
quick look in the Xen manual
(http://tx.downloads.xensource.com/downloads/docs/user/)
comes up
with
this :
>Block
devices should typically only be shared between domains in a
>read-only
fashion otherwise the Linux kernel's file systems will get
>very
confused as the file system structure may change underneath
>them
(having the same ext3 partition mounted rw twice is a sure fire
>way
to cause irreparable damage)! Xend will attempt to prevent you
>from
doing this by checking that the device is not mounted
>read-write
in domain 0, and hasn't already been exported read-write
>to
another domain.
Now,
if you are prepared to do the unionfs stuff in the DomU then I'd
guess
you could export the shared block device read-only to each
guest,
plus a separate read-write volume per guest to union with it.
Looking
at the live CD systems (like Knoppix) might give you some ideas.
--
Simon
Hobson
Visit
http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author
Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas
stocking fillers. Some available as e-books.
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