Linux is a Unix-like operating system, which runs on PC-386 computers. It was implemented first as extension to the Minix operating system [] and its first versions included support for the Minix filesystem only. The Minix filesystem contains two serious limitations: block addresses are stored in 16 bit integers, thus the maximal filesystem size is restricted to 64 mega bytes, and directories contain fixed-size entries and the maximal file name is 14 characters.
We have designed and implemented two new filesystems that are included in the standard Linux kernel. These filesystems, called ``Extended File System'' (Ext fs) and ``Second Extended File System'' (Ext2 fs) raise the limitations and add new features.
In this paper, we describe the history of Linux filesystems. We briefly introduce the fundamental concepts implemented in Unix filesystems. We present the implementation of the Virtual File System layer in Linux and we detail the Second Extended File System kernel code and user mode tools. Last, we present performance measurements made on Linux and BSD filesystems and we conclude with the current status of Ext2fs and the future directions.