Inodes are data structures that contain information about files in Unix and derivative file systems. Each file has an inode and is identified by an inode number (i-number) in the file system where it resides. Inodes provide important information on files such as user and group ownership, access mode (read, write, execute permissions) and type. Inodes are created when a file system is created. There are a set number of inodes, which indicates the maximum number of files the system can hold.