On Wed, 2006-08-23 at 10:02 -0400, Jerry Geis wrote:
> How do I mount a partition that is in an image file?
>
> I have a file called centos.img that has 3 partitions in the file.
> I need to copy data to the third partition on that image file.
>
> I have seen things about a loop back device (which is fine)
> but then it talked about an offset parameter and I dont know what
> that is or more importantly what number to use. I hope I'm on the
> right track.
>
> How do I mount it?
Just assign the whole thing to a loop device. Then do an
"sfdisk -l /dev/loop0" # or whichever loop you used
If it is truly an image file, at that point it *appears* identical to a
real device. I've added little sample I ran, since I know this can be
scary.
Offset is just if you need to start elsewhere from the beginning. If
you're using LVM, you'll have more work to do.
====================================================================
# Pardon my verbosity as I set up a test scenario.
# lvextend --extents +40 VolGroupTemp/LogVol00
Extending logical volume LogVol00 to 1.62 GB
Logical volume LogVol00 successfully resized
mke2fs -b 4096 -m 0 -N 128 /dev/VolGroupTemp/LogVol00
<snip extremely fascinating refs to momentous cosmological events>
Maximum filesystem blocks=436207616
...
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
...
# mount -t ext2 /dev/VolGroupTemp/LogVol00 /VolGroupTemp/LogVol00/
# dd if=/dev/hda of=/VolGroupTemp/LogVol00/hda_image bs=8225280
<snip>
# losetup /dev/loop0 /VolGroupTemp/LogVol00/hda_image
[root@server01 ~]# sfdisk -l -uS /dev/loop0
Disk /dev/loop0: cannot get geometry
Disk /dev/loop0: 0 cylinders, 0 heads, 0 sectors/track
Warning: The partition table looks like it was made
for C/H/S=*/255/63 (instead of 0/0/0).
For this listing I'll assume that geometry.
Units = sectors of 512 bytes, counting from 0
Device Boot Start End #sectors Id System
/dev/loop0p1 * 63 208844 208782 83 Linux
/dev/loop0p2 208845 2506139 2297295 8e Linux LVM
/dev/loop0p3 0 - 0 0 Empty
/dev/loop0p4 0 - 0 0 Empty
# dc
63
512*pq
32256
# losetup -o 32256 /dev/loop1 hda_image
# e2fsck /dev/loop1
e2fsck 1.35 (28-Feb-2004)
/boot: clean, 43/26104 files, 19763/104388 blocks
# mkdir /mnt/temp
# du -s /mnt/temp/* # Snipped below for brevity
51 /mnt/temp/config-2.6.9-34.0.1.EL
211 /mnt/temp/grub
986 /mnt/temp/initrd-2.6.9-34.0.1.EL.img
...
1442 /mnt/temp/vmlinuz-2.6.9-34.0.2.EL
1442 /mnt/temp/vmlinuz-2.6.9-34.EL
# dc
32256
208782
512*+pq
106928640
# losetup -o 106928640 /dev/loop2 hda_image
# pvdisplay /dev/loop2
Found duplicate PV 602X4Js851U78eRzvYP3Fhyf4F8A1v68: using /dev/hda2
not /dev/loop2
Found duplicate PV 602X4Js851U78eRzvYP3Fhyf4F8A1v68: using /dev/loop2
not /dev/hda2
--- Physical volume ---
PV Name /dev/loop2
VG Name VolGroup00
PV Size 1.09 GB / not usable 0
Allocatable yes (but full)
PE Size (KByte) 32768
Total PE 35
Free PE 0
Allocated PE 35
PV UUID 602X4J-s851-U78e-RzvY-P3Fh-yf4F-8A1v68
=================================================================
>
> THanks,
>
> Jerry
> <snip sig stuff>
HTH
--
Bill
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