This article describes how to format and encrypt a disk (technically, a file system). It uses SUSE Linux 11.1 as example, but it should work same or similar with any distribution.
- Start the disk partitioner
- Select a partition you want to format or a disk where you want to add an encrypted partition
- Choose Format partition and "encrypt file system"
- If you get an information that you need to install "pam_mount", allow this
- choose "next"
- enter a password for your system => next => finish