We attached the volume, now let’s get into that virtual machine:
[email protected]:~$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 20G 0 disk └─sda1 8:1 0 20G 0 part / sdb 8:16 0 1G 1 disk sr0 11:0 1 410K 0 rom
[email protected]:~$ sudo dd if=/dev/zero of=/dev/sdb bs=1M count=1 dd: failed to open ‘/dev/sdb’: Read-only file system
Please note that there is nothing to do with the Cinder backend that you use, this operation is done by QEMU itself.
So even if your backend does not support it it does not really matter.
If you look at the libvirt XML of your instance you will see a readonly section.