Create and manage hard links

Learn how Linux file systems use hard links to let multiple directory entries point to the same underlying data. You’ll see how to create, inspect, and remove hard links without wasting disk space.

Files, Inodes, and Link Counts

Every file on a Linux filesystem (ext4, XFS, etc.) is represented by an inode. The inode stores metadata—permissions, timestamps, and pointers to data blocks on disk. The “Links” count in the stat output shows how many directory entries (hard links) reference that inode.

Let’s simulate Aaron saving a photo of his dog:

mkdir -p /home/aaron/Pictures
echo "Picture of Milo the dog" > /home/aaron/Pictures/family_dog.jpg
stat /home/aaron/Pictures/family_dog.jpg

Example output:

File: /home/aaron/Pictures/family_dog.jpg
Size: 24         Blocks: 8          IO Block: 4096   regular file
Device: fd00h/64768d Inode: 52946177    Links: 1
Access: (0640/-rw-r-----)  Uid: (1000/aaron)   Gid: (1005/family)
...

Each new file has one link by default.

Why Use Hard Links?

Copying files duplicates data and consumes extra space:

cp /home/aaron/Pictures/family_dog.jpg /home/jane/Pictures/

Hard links solve this by pointing two filenames to the same inode:

ln /home/aaron/Pictures/family_dog.jpg /home/jane/Pictures/family_dog.jpg

Now both entries share one set of data blocks.

Comparison	Copy (`cp`)	Hard Link (`ln`)
Disk Usage	Duplicated per copy	Single copy on disk
Data Consistency	Separate files	Always the same content
Link Count Effect	Independent inodes	Inode “Links” count increases by 1

Note

Hard links only work on regular files within the same filesystem. See limitations below.

Inspecting Link Counts

After creating the hard link, check the link count again:

stat /home/jane/Pictures/family_dog.jpg

File: /home/jane/Pictures/family_dog.jpg
...
Inode: 52946177    Links: 2
...

Now Links: 2 confirms two directory entries point to the same inode.

Removing Hard Links

If Aaron removes his entry:

rm /home/aaron/Pictures/family_dog.jpg
stat /home/jane/Pictures/family_dog.jpg
# Links: 1

Only when all links are removed does the filesystem reclaim the inode and free the data blocks:
```
rm /home/jane/Pictures/family_dog.jpg
```

Limitations of Hard Links

You cannot:

Link directories (to prevent cycles in the filesystem tree).
Cross filesystem boundaries (e.g., SSD → external drive).

The image illustrates limitations and considerations of hardlinking, showing that hardlinks can only be created for files, not folders, and must be on the same filesystem.

Warning

Attempting to ln a file across different mounts will fail silently or return an error:

ln: failed to create hard link ... Invalid cross-device link

Permissions and Hard Links

Permissions and ownership are stored in the inode itself. Changing them via any hard link affects all links:

chmod g+rw /home/aaron/Pictures/family_dog.jpg
# Applies to /home/jane/Pictures/family_dog.jpg as well

Ensure users have the appropriate permissions in the target directory before creating a hard link.

Watch Video