inode
also: index node, i-node
An inode is a data structure that stores metadata about a file or directory on the filesystem, such as permissions, ownership, timestamps, and pointers to the actual file data—but not the filename itself.
Every file and directory on a Linux filesystem is represented by an inode (index node), which is identified by a unique number called the inode number. The inode stores critical information: file size, permissions (mode), owner (UID/GID), timestamps (created, modified, accessed), and block addresses pointing to where the file's actual data is stored on disk.
Importantly, the filename is not stored in the inode itself—instead, a directory contains entries mapping filenames to inode numbers. This separation allows multiple filenames to point to the same inode (hard links) or lets you rename a file without changing its inode number.
You can view inode information using ls -i to see inode numbers, or stat filename for detailed metadata. For example:
$ ls -i myfile.txt
12345678 myfile.txt