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In this lesson, you’ll learn how Linux uses inodes and hard links to share files efficiently—without duplicating data. We’ll cover:
  • What inodes and links are
  • Creating hard links
  • Deletion behavior
  • Common limitations
  • Permission management
Every file on a Linux filesystem is represented by an inode, which stores metadata (permissions, timestamps, disk block locations). A hard link is simply another directory entry that points to the same inode. Consider Aaron’s photo of his dog Milo, saved as:
Create this sample file and inspect its inode:
Example output:
When you open or read a file, the kernel looks up its name, retrieves the inode (e.g., 52946177), and accesses the data blocks. Hard links simply give you multiple names for the same inode.

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Sharing Files Without Duplication

Copying large directories wastes disk space:
Instead, Jane can create a hard link to Aaron’s photo:
  • Source: /home/aaron/Pictures/family_dog.jpg
  • Link name: /home/jane/Pictures/family_dog.jpg
Verify with stat:
Now the link count is 2:

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Deletion Behavior

When Aaron removes his link, the data remains as long as one hard link exists:
  • Link count drops to 1
  • File content is still intact for Jane
Only when the last link is deleted does the filesystem free the inode and data:
  • You cannot create hard links to directories (prevents filesystem loops).
  • Hard links must reside on the same filesystem—cross-device linking is not allowed.

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Managing Permissions for Shared Files

Since file permissions live in the inode, updating them on one hard link affects all links. To let both Aaron and Jane read/write:
  1. Add both users to a common group (family):
  2. Set group read/write permissions:
Now both can modify the shared file seamlessly.

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Further Reading

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