Loop back mounted files on UBIFS file system

Loop back mounted files on UBIFS file system

[Gilad Ben-Yossef]

Hi All,


I am trying to loop back mount a file (which contains a FAT32 file 
system image), which resides on a UBIFS file system.



Command I try:

*# losetup -o 4096 /dev/loop/0 /mnt/ubifs/fat32
***


Where /nnt/ubifs/ is the mount point of a valid UBIFS file system.


The response I get is:


losetup: /dev/loop/0: No such device or address


Trying a loopback mount from any other file system (such as tmpfs) works.


Trying to do any other activity with the UBIFS file system works as well.


Please note that I am NOT trying to loop back mount a file containing a 
UBIFS file system image and I read the FAQ and understand that this is 
not directly possible, disregarding nandsim. I am trying to do the 
opposite - loopback mount a file residing on an UBIFS file system.


Googling around I've found another post citing what seems like the very 
same behaviour. The answer there was a reference to the above mentioned 
FAQ entry, which I believe is not relevant for the aforementioned reasons.


Kernel version is 2.6.24 with the last back ported UBIFS support. I 
realize that this is an old version and no longer maintained and I'd be 
happy to try the latest and greatest, just wanted to make sure this is 
something that is supposed to work rather then that I am trying to do 
the impossible.



Many thanks,

Gilad

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Re: Loop back mounted files on UBIFS file system

[Adrian Hunter]

Gilad Ben-Yossef wrote:
> Hi All,
> 
> 
> I am trying to loop back mount a file (which contains a FAT32 file 
> system image), which resides on a UBIFS file system.
> 
> 
> 
> Command I try:
> 
> *# losetup -o 4096 /dev/loop/0 /mnt/ubifs/fat32
> ***
> 
> 
> Where /nnt/ubifs/ is the mount point of a valid UBIFS file system.
> 
> 
> The response I get is:
> 
> 
> losetup: /dev/loop/0: No such device or address

I tried it quickly with a recent kernel and also on 2.6.24 

	git://git.infradead.org/users/dedekind/ubifs-v2.6.24.git

and it seemed to work.  I could mount and read and write.

/dev/loop/0 does exist doesn't it?  What does losetup -f say?

> 
> 
> Trying a loopback mount from any other file system (such as tmpfs) works.
> 
> 
> Trying to do any other activity with the UBIFS file system works as well.
> 
> 
> Please note that I am NOT trying to loop back mount a file containing a 
> UBIFS file system image and I read the FAQ and understand that this is 
> not directly possible, disregarding nandsim. I am trying to do the 
> opposite - loopback mount a file residing on an UBIFS file system.
> 
> 
> Googling around I've found another post citing what seems like the very 
> same behaviour. The answer there was a reference to the above mentioned 
> FAQ entry, which I believe is not relevant for the aforementioned reasons.
> 
> 
> Kernel version is 2.6.24 with the last back ported UBIFS support. I 
> realize that this is an old version and no longer maintained and I'd be 
> happy to try the latest and greatest, just wanted to make sure this is 
> something that is supposed to work rather then that I am trying to do 
> the impossible.
> 
> 
> 
> Many thanks,
> 
> Gilad
>