Example for /backstores:/user:qcow

[JosefMissel]

Hello,
i want use "qcow" Backstore and use the command:

/backstores/user:qcow> create cfgstring=/mnt/LUN51 name=lun51 size=51G
'size', 'level', and 'config' must be set when creating a new UserBackedStorageObject

I don't find a way to use "qcow".

apt-cache policy targetcli-fb
targetcli-fb:
Installiert: 2.1.43-1
Installationskandidat: 2.1.43-1
Versionstabelle:
*** 2.1.43-1 500
500 http://ftp.de.debian.org/debian stretch/main amd64 Packages
100 /var/lib/dpkg/status

Thanks