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Re: Talking about loop devices




On Fri, 1 Feb 2019 at 05:50, Pascal Hambourg <pascal@xxxxxxxxxxxxxxx> wrote:
>
> Le 31/01/2019 à 02:15, David a écrit :
> >
> > A *loop* device is a *filesystem* technique to make a file
> > accessible as a block device.
>
> I do not think that loop devices have anything to do with filesystems.
> The losetup(8) manpage states :
>
>         losetup  is  used to associate loop devices with regular files or
>         *block devices* (...)
>
> A use case for a loop device based on another block device is to create
> a partitionable block device when the underlying block device contains a
> raw disk image but is not partitionable (e.g. partition or logical volume).
>
> > ----- begin quote -----
> > The loop devices are used to mount filesystems not
> > associated with block devices.
> > ----- end quote -----
>
> There are other uses. In addition to the use case I mentionned above, a
> loop device can also be used as a swap device when the filesystem does
> not support swap files (e.g. btrfs).

Thanks for clarifying my imprecise language, and adding extra info.