Loopback files on a FAT based Filesystem? Post: 302104298

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Special Forums Hardware Filesystems, Disks and Memory Loopback files on a FAT based Filesystem? Post 302104298 by deckard on Wednesday 24th of January 2007 02:54:38 PM

01-24-2007

Registered User

Loopback files on a FAT based Filesystem?

I'm trying to set up a set of loopback files on a digital music player so I can carry a QEMU virtual machine with me. The digital music player in question is the Rio Karma and the filesystem it uses is omfs. Based on what I read at the Rio Karma FS page: http://linux-karma.sourceforge.net/rio-usb.html it would appear that omfs is based on FAT. One of the things that also seems to support this is that I wasn't able to create loopback files larger than 2 gigs on the filesystem.

The other point to note is that I am coupling omfs with a fuse userspace filesystem 'lkarmafs' which allows one to mount the Karma in "Taxi" mode. This provides a location in <base mount point>/taxi/ that you can carry regular files in. I am able to create loopback files here, but I can't seem to use them as I would if they were on an ext3 or reiserfs partition. So I tried a new approach and create my files at an appropriate size on a ext3 partition. I then prepped them (fdisk/lvm/format) and made sure they stayed below the 2 gig limit. I then copied them to the taxi folder. All of this seemed to work fine.

As soon as I pointed QEMU at those files it complains that it can't read the first file passed to it. But it reads the same exact file on ext3 just fine. So I suspect there is some limitation of either lkarmafs, fuse, omfs or even FAT that prevents proper access to the files. I post this mostly because I'm wondering if any one has any suggestions regarding loopback files on non-Unix filesystems. Perhaps there is an inherent limitation in FAT that prevent loopback from working right? Maybe I created them improperly? Here is the dd command I used:

Code:

dd if=/dev/zero bs=1024 count=2097152 of=1.img

Maybe I should have used 512 for bs? Or am I just barking up the wrong tree and there are too many possible causes to really investigate?

deckard

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LEARN ABOUT SUSE

ocp

OCP(1)                                                        General Commands Manual                                                       OCP(1)

NAME

       ocp - music player

SYNOPSIS

       ocp [ options ] [ playlist ] [ modulename ]

DESCRIPTION

       This manual page documents briefly the ocp command.

       ocp is a music player which can play music modules (it, s3m, xm, mod), wave, audio CD, sid, midi, mp3, adlib, flac, ym, and ogg vorbis.

       The player has a built-in file selector which can be configured using alt-c.  Press f1 for the online help.

       To use the graphical output mode see your ~/.ocp/ocp.ini configuration file.

OPTIONS

       -h     Show summary of options.

       -c     Use specific configuration.

       -f     Fileselector settings

       -v     Sound settings

       -s     Device settings

       -p     Quit when playlist is empty.

EXAMPLE

       ocp -fl0,r1 -vp75,f2 -spdevpdisk -sr48000 fegolhuz.xm

       Renders the module to HD.

SEE ALSO

       You can find a more detailed document at http://www.cubic.org/player/opencp.pdf.
       file:///usr/share/doc/opencubicplayer-doc/
       oggenc(1), flac(1), lame(1).

AUTHOR

       Open Cubic Player was written by Niklas Beisert and ported to Linux by Stian Sebastian Skjelstad.

       This manual page was written by Gurkan Sengun <gurkan@linuks.mine.nu>, for the Debian project (but may be used by others).

                                                                 December 26, 2006                                                          OCP(1)