What an inode is
An inode is a data structure used by many file systems to store information about a file. Crucially, the inode holds the file's details and the location of its actual data, but not the file's name. Each file has an inode that describes it, acting as the file's underlying record. This separation between a file's name and its inode is a central idea in how Unix-like file systems are organized.
What an inode stores
An inode contains the metadata about a file: information such as its size, who owns it, the permissions that control who can access it, timestamps, and pointers to where the file's data actually resides on the storage device. In other words, the inode describes everything about the file except its name and its data content. It is the bookkeeping record that lets the system find and manage the file.
Names versus inodes
In these file systems, a file's name is kept separately, in a directory, which links the name to the file's inode. This means the name is really just a label pointing to an inode. One consequence is that the same underlying file can have more than one name pointing to its inode, and renaming or moving a file within the system can be done by changing directory entries without touching the inode or the data itself.
How inodes are used
When you access a file by name, the system looks up the name in a directory to find the corresponding inode, then uses the inode to locate the file's data and check its permissions. The inode is the key intermediary in this process. Because the system identifies files internally by their inodes rather than their names, it can manage files robustly even as names are added, changed, or removed.
Inodes as a finite resource
A file system has a certain number of inodes, set when it is created, with each file using one. This means that, at least in principle, a file system could run out of inodes even if storage space remains - for example, if it holds an enormous number of very small files. In practice this is uncommon, but it illustrates that inodes are a real, countable resource that the file system manages alongside raw storage space.
Why it matters
Inodes are a foundational concept behind how Unix-like file systems store and organize files. Understanding what an inode is - a record holding a file's metadata and data location, separate from its name - clarifies how files can have multiple names, how the system finds file data, and why names and files are distinct. For anyone curious about how file systems really work, the inode is a key idea.
Related on Skillo
See also: What is a symbolic link? Explained, What is a file system? Explained simply.
Sources
Published date reflects the original event date (2023-07-18). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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