This article is from 2007, I found it to be an excellent and detailed review of the most common tools that exist to encrypt data in Unix systems. These different tools and methods are still valid and in use nowadays. It provides some insights on encryption techniques, code quality, and the relative merits of the [...]

eCryptfs is a cryptographic filesystem embedded inside the Linux kernel (versions 2.6.19 and later), it is also a stacked filesystem, which means that eCryptfs is a layer that works on top of other standard, lower file systems, such as ext4, FAT32, XFS and ReiserFS. Some of the great advantadges of eCryptfs over other encryption methods [...]