Below is part of $ lsblk return: ----------------------------------------- sdb sdb 8:16 ├─sdb1 sdb1 8:17 btrfs poppy-root └─sdb2 sdb2 8:18 -------------------------------------------------- /dev/sdb2 has no filesystem yet, and is not mounted anywhere. Now running this command: ------------------------------------------------------ # make-bcache --block 4k --bucket 2M -B /dev/sdd4 -C /dev/sdb2 --discard Can't open dev /dev/sdb2: Device or resource busy ----------------------------------------------------------- I can't find any reason for /dev/sdb2 to be busy. Thank you for hint. -- google.com/+arnaudgabourygabx