mount: could not find any free loop device

Luciano Rocha strange at
Tue Jun 26 22:42:40 UTC 2007

On Wed, Jun 27, 2007 at 12:28:28AM +0200, Andras Simon wrote:
>  I'm trying to
>  mount -o loop,offset=32256 /usr/local/kvm-images/WinXP.raw /mnt/
>  as I've done successfully several times before, but now I get
>  mount: could not find any free loop device
>  What can possibly use loop devices? There are eight processes called
>  loop0 through loop7, all started by kthread. But I've no idea what
>  they do and if it's them who are using the loop devices.

They're the one serving the loop devices in use. So you exausted the
free loop devices. Free one (umount any in use) and try again.

You can see what is being used by a loop device with losetup:
# losetup /dev/loop0
/dev/loop0: [fd06]:234921356 (/linux/isos/backtrack.iso)

It is possible to increase the number of available loop devices. Free
all loop devices, and add a line with the following to
options loop max_loop=64

(maximum is 256)

Then, do: rmmod loop && modprobe loop

If you get an error that the module couldn't be removed, you still have
loop devices in use.

Newer kernels (2.6.21 or 2.6.22) use a dynamic allocation of loop
devices, so you will only have to create the filesystem representation
of the devices:
for ((i=8;i<64;i++)); do
  [ -e /dev/loop$i ] || mknod -m 0600 /dev/loop$i b 7 $i

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