Private loop devices with loopfs

Posted May 8, 2020 4:44 UTC (Fri) by pabs (subscriber, #43278)
Parent article: Private loop devices with loopfs

Are loop devices part of the device mapper infrastructure or separate to it?

Private loop devices with loopfs

Posted May 8, 2020 13:47 UTC (Fri) by corbet (editor, #1) [Link]

Loop devices predate the device mapper by a long time and are a separate thing.

Private loop devices with loopfs

Posted May 8, 2020 14:36 UTC (Fri) by Sesse (subscriber, #53779) [Link] (2 responses)

dm devices are virtual block devices where the blocks are mapped to other block devices (well, not necessarily directly; they typically go through a module of some sort to add logic). Loopback devices are virtual block devices where the blocks are mapped to a file; think mounting an ISO file as if it were a CD-ROM.

I guess in theory, you could create a loop backend for dm? But they are separate.

Private loop devices with loopfs

Posted May 8, 2020 19:07 UTC (Fri) by dtlin (subscriber, #36537) [Link]

https://www.sourceware.org/lvm2/wiki/DMLoop existed but doesn't look like it was completed or upstreamed.

Private loop devices with loopfs

Posted May 14, 2020 4:35 UTC (Thu) by samuelkarp (subscriber, #131165) [Link]

Docker's devicemapper-based storage driver can be backed by a loopback device.