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Systems & Data Center · Intermediate

Inode

A filesystem data structure storing a file's metadata (owner, permissions, timestamps, block pointers) but not its name.

Definition

Every file on ext4, XFS and similar filesystems has an inode identified by a number; directory entries map names to inode numbers. A filesystem can run out of inodes even with free space remaining, which prevents new files from being created.

Example

ls -i shows inode numbers; df -i reports inode usage per filesystem.

Exam tip

If disk space is free but files cannot be created, suspect inode exhaustion and check with df -i.

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