An inode is where a UNIX-style computer system stores information about files in the system. Each file in the system is tied to one of these nodes, which keeps track of information like ownership, permissions, and file type. Inodes are identified by numbers. Usually about 1 percent of the storage capacity of a file system is used for this type of storage.
UNIX-style computer systems are those descended from the UNIX operating system. They are often used in servers, computer workstations, and mobile devices. UNIX was developed in 1969 by employees of AT&T who were working at Bell labs. Examples of UNIX-based systems include Linux and Berkeley Software Distribution, sometimes known as Berkeley UNIX.
The inode is part of the basic file system of these types of operating systems. A file system organizes computer files and the data relating to them into a database so that the operating system can store, organize, and use them. It uses inodes to store essential information about the file.
The file name is not listed since an individual file can sometimes be accessed using multiple file names. Instead, the inode stores information about which user or group owns the file and which users and groups have permission to read, edit, or use the file. It also stores information about what type the file is.
On most systems only about 1 percent of the file system storage space is used for inodes. This limits the number of files a system can maintain. As a new file is created, new inodes are also created. If the user attempts to create too many files, the storage limit may be reached, preventing the creation of any new files.
As each inode is created, it is assigned a number. This number stays the same when the disk on which the file is located is defragmented, even if this defragment results in the file being moved. If the file is moved manually, the number will also remain the same.
The operating system maintains an inode database. This database is used by the computer to keep track of and access the information in each inode. Files may also be opened by accessing the inode through the database.
A computer user can find the inode of an individual file. He or she can do this by using the ls -i command. This command will cause the inode to display some of the information stored for the file in question.