Linux® Desk Reference, Second Edition

Introduction

In the Linux environment, a file is defined by its inode. Although most users never have occasion to directly access the inode, it is one of the fundamental components of the operating system, and thus it is very useful to have at least a cursory understanding of it.

The inode is a data structure that contains all the information the system needs to know about a particular file. This includes a unique identifying number (the inode number ), the name of the file, its size , the file's location on the device, the most recent access and update times , the file's (numeric) owner and group id s, access permissions , and a pointer to the first block of data the file contains.

In UNIX, everything that isn't a running process is a file. ...