How To Create Symbolic Links Using The ln Command

Symbolic Links
Symbolic Links.

Introduction

In this guide I will show you how to create and use symbolic links using the ln command. 

There are two types of links available:

  • Hard links
  • Soft links

I have previously written a guide already showing what hard links are and why you would use them and so this guide will mainly be focusing on soft links or symbolic links as they are more commonly known.

What Is A Hard Link

Each file in your file system is identified by a number called an inode.

Most of the time you won't really care about this but the importance of this comes to light when you want to create a hard link.

A hard link lets you assign a different name to a file in a different location but essentially it is exactly the same file. The key that links the files together is the inode number.

The great thing about hard links is that they don't take up any physical hard drive space.

A hard link makes it easier to categorise files. For instance imagine you have a folder full of photos. You could create one folder called holiday pictures, another folder called kids photos and a third called pet photos.

It is possible that you will have some photos that fit into all three categories because they were taken on holiday with your children and dogs present.

You could put the main file in the holiday pictures photos and then create a hard link to that photo in the kids photos category and another hard link in the pet photos category.

No extra space is taken up.

All you have to do is enter the following command to create a hard link:

ln /path/to/file /path/to/hardlink

Imagine you had a photo called BrightonBeach in the holiday photos folder and you wanted to create a link in the kids photos folder you would use the following command

ln /holidayphotos/BrightonBeach.jpg /kidsphotos/BrightonBeach.jpg

You can tell how many files link to the same inode by using the ls command as follows:

ls -lt

The output will be something like -rw-r--r-- 1 username groupname date filename.

The first part shows the user's permissions. The important bit is the number after the permissions and before the username. 

If the number is 1 it is the only file pointing to a particular inode (i.e. it is not linked). If the number is greater than one then it is hard linked by 2 or more files.

What Is A Symbolic Link

A symbolic link is like a shortcut from one file to another. The contents of a symbolic link is the address of the actual file or folder that is being linked to.

The benefit of using symbolic links is that you can link to files and folders on other partitions and on other devices.

Another difference between a hard link and a symbolic link is that a hard link must be created against a file that already exists whereas a soft link can be created in advance of the file it is pointing to existing.

To create a symbolic link use the following syntax:

ln -s /path/to/file /path/to/link

If you are worried about overwriting a link that already exists you can use the -b switch as follows:

ln -s -b /path/to/file /path/to/link

This will create a backup of the link if it already exists by creating the same filename but with a tilde at the end (~).

If a file already exists with the same name as the symbolic link you will receive an error.

You can force the link to overwrite the file by using the following command:

ln -s -f /path/to/file /path/to/link

You probably don't want to use the -f switch without the -b switch as you will lose the original file.

Another alternative is to receive a message asking whether you want to overwrite a file if it already exists. You can do this with the following command:

ln -s -i /path/to/file /path/to/link

How do you tell if a file is a symbolic link?

Run the following ls command:

ls -lt

If a file is a symbolic link you will see something like this:

myshortcut -> myfile

You can use a symbolic link to navigate to another folder.

For example imagine you have a link to /home/music/rock/alicecooper/heystoopid called heystoopid

You can run the following cd command to navigate to that folder using the following command:

cd heystoopid

Summary

So that is it. You use symbolic links like shortcuts. They can be used to make really long paths shorter and a way to get easy access to files on other partitions and drives.

This guide shows everything you need to know about symbolic links but you can checkout the manual page for the ln command for the other switches.

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