Difference between Hard Link and Soft Link in Linux

[Shane]

Hard Link is a mirror copy of the original file. Hard links share the same inode.
Any changes made to the original or Hard linked file will reflect the other.
Even if you delete any one of the files, nothing will happen to the other.
Hard links can't cross file systems.

Soft Link is a symbolic link to the original file. Soft Links will have a different Inode value.
A soft link points to the original file. If you delete the original file, the soft link fails. If you delete the soft link, nothing will happen.
Hard links can cross file systems.

Lets learn the difference with an example

Example: Create a file " original-file.txt "

Code: Select all

:~/test$ echo "Learning about Hard and Soft Link" > original-file.txt
:~/test$ cat original-file.txt 
Learning about Hard and Soft Link

Now lets create a Hard Link

Example: HardLink-file.txt

Code: Select all

:~/test$ ln original-file.txt HardLink-file.txt
:~/test$ ls -il
total 8
840388 -rw-r--r-- 2 telson telson 33 2009-05-18 09:16 HardLink-file.txt
840388 -rw-r--r-- 2 telson telson 33 2009-05-18 09:16 original-file.txt

Now lets create a Soft Link

Example: SoftLink-file.txt

Code: Select all

:~/test$ ln -s original-file.txt SoftLink-file.txt
:~/test$ ls -il
total 8
840388 -rw-r--r-- 2 telson telson 33 2009-05-18 09:16 HardLink-file.txt
840388 -rw-r--r-- 2 telson telson 33 2009-05-18 09:16 original-file.txt
840186 lrwxrwxrwx 1 telson telson 17 2009-05-18 09:23 SoftLink-file.txt -> original-file.txt

From the above ls -il result, you find the same inode for " HardLink-file.txt " and " original-file.txt ".
Inode value is different for the soft link " SoftLink-file.txt ".

Now lets try editing the original file:

Example:

Code: Select all

:~/test$ cat >> original-file.txt 
Editing this file to learn more!!

:~/test$ cat original-file.txt 
Learning about Hard and Soft Link
Editing this file to learn more!!

:~/test$ cat HardLink-file.txt 
Learning about Hard and Soft Link
Editing this file to learn more!!

:~/test$ cat SoftLink-file.txt 
Learning about Hard and Soft Link
Editing this file to learn more!!

Now lets try changing the permissions:

Example:

Code: Select all

:~/test$ chmod 700 original-file.txt 
:~/test$ ls -il
total 8
840388 -rwx------ 2 telson telson 67 2009-05-18 09:34 HardLink-file.txt
840388 -rwx------ 2 telson telson 67 2009-05-18 09:34 original-file.txt
840186 lrwxrwxrwx 1 telson telson 17 2009-05-18 09:23 SoftLink-file.txt -> original-file.txt

From the above example its clear that changing the permission of " original-file.txt " will update the permission set of " HardLink-file.txt ".
The soft link remains unchanged.

Now lets try deleting the original file.

Example:

Code: Select all

:~/test$ rm original-file.txt 
:~/test$ ls -il
total 4
840388 -rwx------ 1 telson telson 67 2009-05-18 09:34 HardLink-file.txt
840186 lrwxrwxrwx 1 telson telson 17 2009-05-18 09:23 SoftLink-file.txt -> original-file.txt

:~/test$ cat HardLink-file.txt 
Learning about Hard and Soft Link
Editing this file to learn more!!

:~/test$ cat SoftLink-file.txt 
cat: SoftLink-file.txt: No such file or directory

So removing the original file will affect the Soft link. The Soft link fails.
Hard link is unaffected.