What is Soft Link And Hard Link In Linux?

A symbolic or soft link is an actual link to the original file, whereas a hard link is a mirror copy of the original file. If you delete the original file, the soft link has no value, because it points to a non-existent file. But in the case of hard link, it is entirely opposite. Even if you delete the original file, the hard link will still has the data of the original file. Because hard link acts as a mirror copy of the original file.

In a nutshell, a soft link

can cross the file system,

allows you to link between directories,

has different inode number and file permissions than original file,

permissions will not be updated,

has only the path of the original file, not the contents.

A hard Link

can't cross the file system boundaries (i.e. A hardlink can only work on the same filesystem),

can't link directories,

has the same inode number and permissions of original file,

permissions will be updated if we change the permissions of source file,

has the actual contents of original file, so that you still can view the contents, even if the original file moved or removed.

Still don't get it? Well, allow me to show you some practical examples.

Creating Soft Link or Symbolic Link

Let us create an empty directory called "test".

$ mkdir test

Change to the "test" directory:

$ cd test

Now, create a new file called source.file with some data as shown below.

$ echo "Welcome to OSTechNix" >source.file

Let us view the data of the source.file.

$ cat source.file Welcome to OSTechNix

Well, the source.file has been created.

Now, create the a symbolic or soft link to the source.file.

To do so, run:

$ ln -s source.file softlink.file

Let us compare the data of both source.file and softlink.file.

$ cat source.file Welcome to OSTechNix

$ cat softlink.file Welcome to OSTechNix

As you see in the above output, softlink.file displays the same data as source.file.

Let us check the inodes and permissions of softlink.file and source.file.

$ ls -lia

Sample output:

total 12 11665675 drwxrwxr-x 2 sk sk 4096 Oct 17 11:39 . 4325378 drwxr-xr-x 37 sk sk 4096 Oct 17 11:39 .. 11665731 lrwxrwxrwx 1 sk sk 11 Oct 17 11:39 softlink.file -> source.file 11665692 -rw-rw-r-- 1 sk sk 21 Oct 17 11:39 source.file

As we see in the above screenshot, the inode number (11665731 vs 11665692) and file permissions (lrwxrwxrwx vs -rw-r--r--) are different, even though the softlink.file has same contents as source.file, . Hence, it is proved that soft link don't share the same inode number and permissions of original file.

Now, remove the original file (i.e source.file) and see what happens.

$ rm source.file

Check contents of the softlink.file using command:

$ cat softlink.file

Sample output:

cat: softlink.file: No such file or directory

As you see above, there is no such file or directory called softlink.file after we removed the original file (i.e source.file). So, now we understand that soft link is just a link that points to the original file. The softlink is like a shortcut to a file. If you remove the file, the shortcut is useless.

As you already know, if you remove the soft link, the original file will still be available.

Suggested read:

Creating Hard Link

Create a file called source.file with some contents as shown below.

$ echo "Welcome to OSTechNix" >source.file

Let us verify the contents of the file.

$ cat source.file Welcome to OSTechNix

source.file has been created now.

Now, let us create the hard link to the source.file as shown below.

$ ln source.file hardlink.file

Check the contents of hardlink.file.

$ cat hardlink.file Welcome to OSTechNix

You see the hardlink.file displays the same data as source.file.

Let us check the inode and permissions of hardlink.file and source.file.

$ ls -lia

Sample output:

total 16 11665675 drwxrwxr-x 2 sk sk 4096 Oct 17 11:58 . 4325378 drwxr-xr-x 37 sk sk 4096 Oct 17 11:39 .. 11665692 -rw-rw-r-- 2 sk sk 21 Oct 17 11:57 hardlink.file 11665692 -rw-rw-r-- 2 sk sk 21 Oct 17 11:57 source.file

Now, we see that both hardlink.file and source.file have the same the inodes number (11665692) and file permissions (-rw-r--r--). Hence, it is proved that hard link file shares the same inodes number and permissions of original file.

Note: If we change the permissions on source.file, the same permission will be applied to the hardlink.file as well.

Now, remove the original file (i.e source.file) and see what happens.

$ rm source.file

Check contents of hardlink.file using command:

$ cat hardlink.file

Sample output:

As you see above, even if I deleted the source file, I can view contents of the hardlink.file. Hence, it is proved that Hard link shares the same inode number, the permissions and data of the original file.

So, what is the difference between Hard link and the normal copied file?

You might be wondering why would we create a hard link while we can easily copy/paste the original file? Creating a hard link to a file is different than copying it.

If you copy a file, it will just duplicate the content. So if you modify the content of a one file (either original or hard link), it has no effect on the other one. However if you create a hard link to a file and change the content of either of the files, the change will be be seen on both. Let us have a look at the source.file. $ cat source.file Welcome to OSTechNix

The source file has a single line that says - Welcome to OSTechNix.

Append a new line, for example "Welcome to Linux" in source.file or hardlink.file.

$ echo "Welcome to Linux" >>source.file

Now check contents of both files.

$ cat hardlink.file Welcome to OSTechNix Welcome to Linux

$ cat source.file Welcome to OSTechNix Welcome to Linux

See? The changes we just made on source.file are updated in both files. Meaning - both files (source and hard link) synchronizes. Whatever changes you do in any file will be reflected on other one. If you normally copy/paste the file, you will not see any new changes in other file.

For more details, check the man pages.

$ man ln

That's all for now. Hope you got a basic idea about symbolic or soft link and hard link.