local mounting of a drive formated byan initiator]

From: Dr. Net! - Eugen Rieck <[email protected]>
To: [email protected]
Subject: Re: [Iscsitarget-devel] RE:local mounting of a drive formated byan initiator
Date: Tue, 23 Aug 2005 21:36:41 +0200
Hi all - solution found.

Quoted 4 lines

Quoted 4 lines

so u export /dev/sda3 to ini side as a DISK, which is not a partition any more. then partition it, use it, and disconnect from it.

but at local side, u can not access a partition in a partition. :P

Exporting the whole disk sda is not the perfect solution - when you export a raid (mdX) you have the same problem, BUT:

No need for kpartx. There is an easy solution to this - use a loop device!

A Partition is nothing else than a continuous part of the underlying block device - so you can touch it with a loop device with offset and size limit.

I assume you exported /dev/sda3 via IET

So you:
1.) Get the partition geometry - You only need to do this once

fdisk -lu /dev/sda3
You see something like

Disk /dev/sda3: 180.0 GB, 180034928640 bytes
255 heads, 63 sectors/track, 21888 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda3p1 63 351614654 175807296 7 HPFS/NTFS

Note the Start (63) and End (351614654 ) Values - they tell you, that inside sda3 your "partition in a partition" starts at sector 63 and ends at sector 351614654
So:
Offset=63 Blocks=63*512=32256
Length=351614654 -63+1=351614592 Blocks=180026671104 Bytes

If you use the last partition up to the end of the disk, you don't need the length, but I'll take it here for clarity

2.) Get a free loop device - you have to do this for every boot (I'll fix up a script to automate it and follow up later)

Variante 1 (New versions of losetup):
losetup -a
You see something like
/dev/loop0: [0805]:1740 (/var/install/suse93.dvd)
/dev/loop7: [0805]:2065 (/var/tmp/aoe/volume)

You now know, that loop devices 0 and 7 are in use, making 1-6 free. No output means all loop devices are free

Variante 2 (if 1 fails on older versions):
If losetup -a complains, you have an older version that dosesn't understand the -a flag. in this case do
losetup /dev/loop0
losetup /dev/loop1
...
until you get "no such device or address" - again you have found a free loop device.

I now assume that loop1 is free

3.) set up the loop device

losetup -o 32256 -s 180026671104 /dev/loop1 /dev/sdc3

(quoted diff) +0 -2

-o 32256 is offset from 1.)
-s 180026671104 is length from 1.)

/dev/loop1 is free loop device from 2.)
/dev/sdc3 is your exported volume

4.) mount the loop device

mount /dev/loop1 /your/mount/point

Done!

I just tried this with my box - this is where the numbers come from

Have fun!

Regards, Eugen

:-) Eugen Rieck (-:
[email protected]

Programmer: Biological device,
designed to convert coffee into code

-------------------------------------------------------
SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf
_______________________________________________
Iscsitarget-devel mailing list [email protected]
https://lists.sourceforge.net/lists/listinfo/iscsitarget-devel