Hard & Symbolic Links

The ln command is used to create links between files. There are two types of links: HardLinks & Symbolic Links

ln [options] {target name} [link name]

Hard Links

• A hard link is an additional name for an existing file.

• Points directly to the inode (underlying data).

• All hard links to a file are equal – there's no "original" vs "copy".

• If the original file is deleted, the data remains as long as one hard link still exists.

• You cannot create hard links between directories.
• You cannot create hard links between different filesystems.

ln sourcefile link_name

Visual representation of a hard link:

[file1] ─┐
         │
[inode X]──> "hello"
         │
[file2] ─┘

Recognising Hard Links

When a file has a hard link on it, the OS doesn't make it massively obvious. IE when you set a symbolic link, it will be obvious when viewing the file that there's an existing link:

lrwxrwxrwx  1 root root       9 Jun 16 14:21 test3.txt -> test1.txt

But hard links don't show this. Instead, the best way to check if 2 files are hard-linked would be to check their inode numbers using ls -li

Symbolic Links

A symbolic link is a pointer or shortcut to another file or directory. It stores the path to the target, not the data itself.

ln -s target link_name

ln -s /etc/config.cfg ~/myconfig