[Fedora-xen] Createing/working with disk images

[Lamont Peterson]

On Tuesday 27 March 2007 03:58pm, Andrew Cathrow wrote:
> Run kpartx to create the devices - will be created in /dev/mapper

Hmm.  I'd run into something that mentioned the use of kpartx (I think is was 
in some openSUSE 10.2 Xen documentation), but looking at it's man page, it 
didn't look like the right tool to create the devices.

> kpartx -a /dev/loop0

So, I'm supposed to:

1.  Create the image file.
2.  Run "losetup /dev/loop0 /whatever/path/to/the/imagefile"
3.  Run "fdisk /dev/loop0" to create the partitions.
4.  Run "kpartx -a /dev/loop0" which will create /dev/mapper/* devices for the 
partitions on /dev/loop0.

Have I got that right?

> On Tue, 2007-03-27 at 15:32 -0600, Lamont Peterson wrote:
> > All,
> >
> > I need to create some images that pygrub can boot (on FC6 & RHEL5). 
> > IIUC, that means that the image file must be a disk image complete with
> > partition table.
> >
> > The trouble I'm running into is figuring out how to access the
> > "partition" within the disk image file as a block device.  This is
> > necessary in order to format or mount the filesystems and run mkswap for
> > the disk image's swap partition.
> >
> > Here's what I have so far.
> >
> > 1.  Create the disk image file, ala "dd if=/dev/zero
> > of=/var/lib/xen/images/someVM/sda bs=1k seek=4608k count=1"
> >
> > 2.  Create partitions with fdisk (this requires setting the number of
> > cylinders, but that's easy).
> >
> > 3.  losetup /dev/loop0 /var/lib/xen/images/someVM/sda
> >
> > At this point, I can run "fdisk -l /dev/loop0" and get:
> >
> > Disk /dev/loop0: 4831 MB, 4831839232 bytes
> > 255 heads, 63 sectors/track, 587 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> >
> >       Device Boot      Start         End      Blocks   Id  System
> > /dev/loop0p1               1         523     4200966   83  Linux
> > /dev/loop0p2             524         588      522112+  82  Linux swap /
> > Solaris
> >
> > However, there is no /dev/loop0p1 or /dev/loop0p2 devices and I'm not
> > sure what to do to make those accessible.  I need to be able
> > to "mke2fs -j /dev/loop0p1" and "mkswap /dev/loop0p2" or equivalent. 
> > Then I need to mount /dev/loop0p1 to copy files to it.
> >
> > How can I access partitions inside a disk image as block devices?  Should
> > I be using something other than losetup here?
> > --
> > Fedora-xen mailing list
> > Fedora-xen at redhat.com
> > https://www.redhat.com/mailman/listinfo/fedora-xen

-- 
Lamont Peterson <lamont at gurulabs.com>
Senior Instructor
Guru Labs, L.C. [ http://www.GuruLabs.com/ ]

NOTE:  All messages from this email address should be digitally signed with my
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