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Re: Talking about loop devices

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).