[Buildroot] losetup /dev/loop0: No such device or address

[Buildroot] losetup /dev/loop0: No such device or address

[Mike Sander]

Hi All,

Im using buildroot-2009.02 on atmel at91sam9g20ek.  It is a fairly stock 
cofiguration. 

When I execute "losetup /dev/loop0 /mnt/flash/backing_file.vfat" i get 
the error "losetup /dev/loop0: No such device or address".    /mnt/flash 
exist and has a mounted jffs2 filesystem on it.As far as I can tell, it 
is working correctly.  I can read/write files. I have checked all the 
obvious suspects (including erroneous error message)

here is the output from mount
# mount                      
rootfs on / type rootfs (rw)
proc on /proc type proc (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /tmp type tmpfs (rw)
sysfs on /sys type sysfs (rw)
/dev/mtdblock2 on /mnt/flash type jffs2 (rw)

looks like a valid mounted filesystem.

# ls /mnt/flash
backing_file.vfat  hosts

the file I am trying to connect to loop0 definately exists.  I copied 
/etc/hosts to it to verify read/write operation.


here are the /dev/loop* devices
# ls -atl loop*
brw-r-----    1 root     root       7,   0 Dec 31 17:00 loop0
brw-r-----    1 root     root       7,   1 Dec 31 17:00 loop1
 
/dev/loop0 definitely exists and appears to be correctly defined (I think).

Anyone aware of issues using losetup?   Is there some obscure dependency 
I might be missing.  any suggestions on how to debug this short of 
printf() from losetup code?

Regards,

mike

[Buildroot] losetup /dev/loop0: No such device or address

[Andreas Schweigstill]

Hello!

Mike Sander  wrote:
> When I execute "losetup /dev/loop0 /mnt/flash/backing_file.vfat" i get 
> the error "losetup /dev/loop0: No such device or address". 

> [...]

> /dev/loop0 definitely exists and appears to be correctly defined (I think).

It just means that the device file exists which is independend of the kernel
handler for block device (7,x).

So you should check your Linux kernel configuration. Loopback device
support has to be enabled in .config:

CONFIG_BLK_DEV_LOOP=y

And in /sys/block also some entries have to be present, normally
/sys/block/loop0 to /sys/block/loop7.

Regards
Andreas Schweigstill

-- 
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Dipl.-Phys. Andreas Schweigstill
Schweigstill IT | Embedded Systems
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Mobile: (+49) 171 6921973, Web: http://www.schweigstill.de/

[Buildroot] losetup /dev/loop0: No such device or address

[Mike Sander]

Andreas Schweigstill wrote:
> Hello!
>
> Mike Sander  wrote:
>   
>> When I execute "losetup /dev/loop0 /mnt/flash/backing_file.vfat" i get 
>> the error "losetup /dev/loop0: No such device or address". 
>>     
>
>   
>> [...]
>>     
>
>   
>> /dev/loop0 definitely exists and appears to be correctly defined (I think).
>>     
>
> It just means that the device file exists which is independend of the kernel
> handler for block device (7,x).
>
> So you should check your Linux kernel configuration. Loopback device
> support has to be enabled in .config:
>
> CONFIG_BLK_DEV_LOOP=y
>   
Andreas, that was what I was missing. 
thanks.
> And in /sys/block also some entries have to be present, normally
> /sys/block/loop0 to /sys/block/loop7.
>
> Regards
> Andreas Schweigstill
>
>