On Sun, 10 Jul 2005, octane wrote:
Jim C. Brown a écrit :
I have some trouble using losetup to mount partitions
from the host.
I never realized how difficult it was to interpret error messages written
in
a foreign language.
Ok, sorry, in plain english messages are:
[EMAIL PROTECTED]:/usr/src/qemu-test# fdisk -l zipslack.img
You must set cylinders.
You can do this from the extra functions menu.
Disk zipslack.img: 0 MB, 0 bytes
16 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes
Device Boot Start End Blocks Id System
zipslack.img1 1 66 33232+ 82 Linux swap
zipslack.img2 67 609 273672 83 Linux
[EMAIL PROTECTED]:/usr/src/qemu-test#
and mounting the file with an offset of $((67*512)) doesn't work
The offset if 67*516096, as this partition table is printed in cylinders,
not sectors.
When calculating partition offsets it is always best to look at the
partition table in sectors, not cylinders, especially considering that
partitions does not need to start exactly on a cylinder boundary. For
example the first partition doesn't start at cylinder 1, it starts at
cylinder 1 head 2, or sector 64. Both fdisk and sfdisk supports viewing
the sector based partition values, maintaining sanity.
I really recommend using lomount or some similar tool to figure out these
offsets for you. (Incidently, lomount doesn't care about disk geometry - it
uses the absolute sector values in the partition table.)
Nearly nobody except for DOS (and the parts of BIOS used by DOS) cares
about geometry..
I receive a mail that says:
fdisk -l zipslack.img is not the same as fdisk- lu zipslack :
[EMAIL PROTECTED]:/usr/src/qemu-test# fdisk -lu zipslack.img
You must set cylinders.
You can do this from the extra functions menu.
Disk zipslack.img: 0 MB, 0 bytes
16 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Device Boot Start End Blocks Id System
zipslack.img1 63 66527 33232+ 82 Linux swap
zipslack.img2 66528 613871 273672 83 Linux
and incidently $((66*516096))=$((66528*512))
Correct, from the cylinders/heads/sectors geometry. If you look at the
swap partition then things is more interesting.. (also why sfdisk printed
a + there, and probably what the + in the blocks column of fdisk
refers to...)
Regards
Henrik
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