[Fedora-xen] Createing/working with disk images

[Andrew Cathrow]

Run kpartx to create the devices - will be created in /dev/mapper

kpartx -a /dev/loop0


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?
> --
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