LUKS is the acronym of Linux Unified Key Setup: it is the most used encryption implementation used on Linux systems and can be configured as an alternative to dm-crypt plain setup. Compared with the latter it provides some additional features like password hashing and salting and the ability to store multiple passwords in the so called LUKS header. In this tutorial I will assume the reader has a certain familiarity with LUKS; if you want to know more about this subject, you can check our basic guide about encrypting linux partitions with luks.
This is a companion discussion topic for the original entry at https://linuxconfig.org/how-to-use-a-file-as-a-luks-device-key