[Fedora-xen] Createing/working with disk images

[Lamont R. Peterson]

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?
-- 
Lamont Peterson <lamont(a)gurulabs.com&gt;
Senior Instructor
Guru Labs, L.C. [ http://www.GuruLabs.com/ ]

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