cryptsetup: simplify page (#953)

- Cited actual examples rather than placeholder text
- Added the 'close' command

pages/linux/cryptsetup.md

@@ -1,11 +1,15 @@
 # cryptsetup
 
-> Manage plain dm-crypt and LUKS encrypted volumes.
+> Manage plain dm-crypt and LUKS(Linux Unified Key Setup) encrypted volumes.
 
-- Format a drive (or a file) to make it a LUKS volume:
+- Initialize a LUKS volume (overwrites all data on the partition):
 
-`cryptsetup luksFormat {{path/to/luks_volume_to_be}}`
+`cryptsetup luksFormat {{/dev/sda1}}`
 
-- Open a volume so that you can access it decrypted on the fly at /dev/mapper/{{a}}:
+- Open a LUKS volume and create a decrypted mapping at /dev/mapper/{{target}}:
 
-`cryptsetup luksOpen {{path/to/luks_volume_to_be}} {{a}}`
+`cryptsetup luksOpen {{/dev/sda1}} {{target}}`
+
+- Remove an existing mapping:
+
+`cryptsetup luksClose {{target}}`