Links to a file

A link to a file means referring the same file by different filenames. In Linux and Unix-based system, the following two types of links exist:

  • A soft link or a symbolic link
  • A hard link

To create links between files, the ln command can be used. The syntax is as follows:

ln [option] target link_name

Here, target is the filename for which a link has to be created and link_name is the name by which a link has to be created.

Soft link

A soft link is a special kind of file that just points to another file. This makes it easier to create a shortcut of a file and easy accessibility of a file to a different location in a filesystem.

To create a symbolic link of a file, the ln command is used with the -s option. For example, we will create a symbolic link of the /tmp directory in our home directory:

$ ln -s /tmp ~/local_tmp

Now, we have a symbolic link of the /tmp directory in our home directory by the name local_tmp. To access the /tmp data, we can also cd into the ~/local_tmp directory. To know whether a file is a symbolic link or not, run ls -l on a file:

$ ls -l ~/local_tmp
lrwxrwxrwx. 1 foo foo 5 Aug 23 23:31 /home/foo/local_tmp -> /tmp/

If the first character of the first column is l, then it means it is a symbolic link. Also the last column says /home/foo/local_tmp -> /tmp/, which means local_tmp is pointing to /tmp.

Hard link

A hard link is a way to refer a file with different names. All such files will have the same inode number. An inode number is an index number in an inode table that contains metadata about a file.

To create a hard link of a file, use the ln command without any option. In our case, we will first create a regular file called file.txt:

$ touch file.txt
$ ls -l file.txt
-rw-rw-r--. 1 foo foo 0 Aug 24 00:13 file.txt

The second column of ls tells the link count. We can see that currently it is 1.

Now, to create a hard link of file.txt, we will use the ln command:

$ ln file.txt hard_link_file.txt

To check whether a hard link is created for file.txt, we will see its link count:

$ ls -l file.txt
-rw-rw-r--. 2 foo foo 0 Aug 24 00:13 file.txt

Now, the link count is 2 because a hard link has been created with the name hard_link_file.txt.

We can also see that the inode number of the file.txt and hard_link_file.txt files are the same:

$ ls -i file.txt hard_link_file.txt
96844   file.txt
96844   hard_link_file.txt

Difference between hard link and soft link

The following table shows a few important differences between a hard link and a soft link:

Soft link

Hard link

The inode number of the actual file and the soft link file are different.

The inode number of the actual file and the hard link file are the same.

A soft link can be created across different filesystems.

A hard link can only be created in the same filesystem.

A soft link can link to both regular files and directories.

A hard link doesn't link to directories.

Soft links are not updated if the actual file is deleted. It keeps pointing to a nonexistent file.

Hard links are always updated if the actual file is moved or deleted.

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