losetup: added example for --read-only and --partscan (#3792)

pages/linux/losetup.md

@@ -17,3 +17,11 @@
 - Detach a given loop device:
 
 `sudo losetup -d /dev/{{loop}}`
+
+- Attach a file to a new free loop device and scan the device for partitions:
+
+`sudo losetup --show --partscan -f /{{path/to/file}}`
+
+- Attach a file to a read-only loop device:
+
+`sudo losetup --read-only /dev/{{loop}} /{{path/to/file}}`