[Fedora-xen] Createing/working with disk images
Lamont Peterson
lamont at gurulabs.com
Tue Mar 27 21:32:30 UTC 2007
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 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
0xDC0DD409 GPG key. It is available on the pgp.mit.edu keyserver as
well as other keyservers that sync with MIT's.
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