A file system depends on data structures about the files, beside the file structure. The former is named metadata-data that defines data. Each file is accumulated with an inode, which is defined by an integer number, usually referred to as an Inode or i-number number.

Inodes locate information about directories and files, such as file ownership, access mode, and file type. On many kinds of file system implementations, the maximum number of inodes is situated at file system limiting, creation the maximum number of files the file system can access. A typical allocation for inodes in a file system is one part of total size.

The inode number indexes a table of inodes in a named location on the device; from the inode number, the file machine driver portion of the kernel may use the contents of the inode, adding the location of the file giving access to the file.

File directory and names operations:

• inodes do not have file names, only file metadata.
• Unix folders are lists of association structures, each of which have one inode and one filename number.
• The file system driver has to search a directory looking for a particular inode and then change the filename to the correct corresponding inode number.

The operating system kernel's in-memory presentation of this data is named struct inode in Linux. Systems operated from BSD use the term vnode, with the v of vnode accessing to the kernel's virtual file system layer.