Unix - Hard Links vs Soft Links in Unix

In Unix and Linux file systems, links are used to create references to files. There are two main types of links: hard links and soft links (symbolic links). Although both point to files, they work very differently at the filesystem level.

Hard Links

A hard link is an additional directory entry that points to the same inode as the original file. Both the original file and the hard link are equal references to the same data on disk.

Key characteristics:

• Shares the same inode number as the original file

• Works only within the same filesystem

• Cannot be created for directories (for safety reasons)

• If the original file is deleted, the data remains accessible through the hard link

Example:

ln file1 file1_hard

Here, file1 and file1_hard are indistinguishable; deleting one does not remove the actual data until all hard links are removed.

Soft Links (Symbolic Links)

A soft link is a special file that contains the path to another file or directory, not the inode itself. It acts like a shortcut or pointer.

Key characteristics:

• Has a different inode number

• Can link across different filesystems

• Can link to directories

• If the original file is deleted, the soft link becomes broken (dangling link)

Example:

ln -s file1 file1_soft

If file1 is removed, file1_soft will no longer work because it points to a non-existent path.

Key Differences at a Glance

When to Use Which

• Use hard links when you need multiple stable references to the same file data and want it to persist even if one name is removed.

• Use soft links when you need flexibility, cross-filesystem linking, or directory references.

In summary, hard links are inode-level references, while soft links are path-based pointers, and understanding this distinction is crucial for effective Unix filesystem management.