Creating file links linux

How to create a link in Linux

In your Linux file system, a link is a connection between a file name and the actual data on the disk. There are two main types of links that can be created: «hard» links, and «soft» or symbolic links. Hard links are low-level links which the system uses to create elements of the file system itself, such as files and directories.

Most users do not want to create or modify hard links themselves, but symbolic links are a useful tool for any Linux user. A symbolic link is a special file that points to another file or directory, which is called the target. Once created, a symbolic link can be used in place of the target file name. It can have a unique name, and be located in any directory. Multiple symbolic links can even be created to the same target file, allowing the target to be accessed by multiple names.

The symbolic link is a file in its own right, but it does not contain a copy of the target file’s data. It is similar to a shortcut in Microsoft Windows: if you delete a symbolic link, the target is unaffected. Also, if the target of a symbolic link is deleted, moved, or renamed, the symbolic link is not updated. When this happens, the symbolic link is called «broken» or «orphaned,» and will no longer function as a link.

How to create symbolic links using a file manager

One way to create a symbolic link in the X Windows GUI is with your file manager. Some Linux distributions use different file managers, but the process is similar. Locate a target file in your file manager GUI, highlight it by clicking it once, and select the «create a link» option. This option is usually found under the Edit menu, or in the context menu that appears when you right-click the highlighted file.

In the example shown above, using the Thunar file manager, we have highlighted the file myfile.txt, then selected Make Link in the Edit menu. After completed, a new symbolic link called link to myfile.txt is created. This link can be renamed or moved to another location. It always points to the target, unless the target is later moved or deleted, resulting in the link becoming orphaned.

How to create symbolic links from the command line

The command line is a powerful tool in Linux because it gives you greater control over your commands. (For more information about the command line, and how to access it from Linux, see our Linux and Unix shell tutorial).

You can create symbolic links using the ln command’s -s option. The general syntax for creating a symbolic link is:

For instance, if we have a file in our working directory called myfile.txt, and we want to create a symbolic link in the same directory called mylink, we could use the command:

In this command, we have opened a terminal session that places us at our shell’s command prompt. We are logged in a system named myhost as a user named user, and our working directory is a folder in our home directory called myfolder:

First, let’s use ls with the -l option to produce a long list of all the files in our directory:

We see our file, myfile.txt, which is the only file in the directory. («total 4» refers to how many blocks on the disk are used by the files listed, not the total number of files).

Let’s use the cat command to view the contents of myfile.txt:

Now, let’s create a symbolic link to mylink.txt called mylink using the ln -s command:

It seems like nothing happened, but this means it worked as expected. If there was an error, or if an unexpected condition was encountered, we would receive a notification.

Now, if we do another ls -l, we see two files — our target and our link:

One of the benefits of doing a long listing with «-l» is that we see extra information in addition to the file name. Notice the «l» at the beginning of the line containing our link name, indicating that the file is a symbolic link. Also, after mylink (in blue text) is the «->» symbol, followed by the name of the target.

Most shells, by default, are configured to display certain file types in different colors, but your terminal might show different colors or none at all.

Now, let’s use our symbolic link. If we run cat on it, it displays the contents of myfile.txt:

We can rename our link with mv, and it still points to the same target:

But what happens if we move our link somewhere else? In this case, our link breaks. We can see this by making a new directory using mkdir, and moving the link into the new directory using mv:

You can see that when we view the contents of directory newfolder with ls -l, our link is highlighted in red, indicating that it is a broken link. If we try to cat the contents of the link, the shell informs us that the file does not exist. It points to «myfile.txt» with no other path information. Therefore, the operating system looks for myfile.txt in the same directory as the link.

Let’s start over by removing newfolder and its contents using the command rm -r:

This time, let’s create the symbolic link using the absolute path to myfile.txt. Let’s double check the name of our working directory using pwd:

Our working directory is /home/user/myfolder, so let’s include this in the target name when we create the link:

As you can see from the output of ls -l, our link now points to the file /home/user/myfolder/myfile.txt. With this path information, we can move the link to another location, and it still points to our target:

Your bash shell keeps an environment variable called $PWD that always stores the value of your working directory. You can use this variable to insert the full path before your target name, as long as the target is in your working directory. We can view the value of $PWD using the echo command:

This text is inserted if we use $PWD as part of a command. It is a good idea to enclose it in quotes as «$PWD» in case the directory name has any spaces. The quotes make sure the shell knows they are part of the pathname and not command separators.

Here is our command, and a directory listing to show that it worked:

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How to: Linux / UNIX create soft link with ln command

Symbolic links can be made to directories as well as to files on different filesystems or different partitions.

Two types of links

• symbolic links (also known as “soft links” or “symlinks”): Refer to a symbolic path indicating the abstract location of another file.
• hard links : Refer to the specific location of physical data.

How do I create soft link / symbolic link under Unix and Linux?

Soft links are created with the ln command. For example, the following would create a soft link named link1 to a file named file1, both in the current directory
$ ln -s file1 link1
To verify new soft link run:
$ ls -l file1 link1
Sample outputs:

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From the above outputs it is clear that a symbolic link named ‘link1’ contains the name of the file named ‘file1’ to which it is linked.

How to use the ln command

So the syntax is as follows to create a symbolic link in Unix or Linux, at the shell prompt:
$ ln -s < source-filename >< symbolic-filename >

For example create a softlink for /webroot/home/httpd/test.com/index.php as /home/vivek/index.php, enter the following command:
$ ln -s /webroot/home/httpd/test.com/index.php /home/vivek/index.php
$ ls -l
Sample outputs:

You can now edit the soft link named /home/vivek/index.php and /webroot/home/httpd/test.com/index.php will get updated:
$ vi /home/vivek/index.php
Your actual file /webroot/home/httpd/test.com/index.php remains on disk even if you deleted the soft link /home/vivek/index.php using the rm command:
$ rm /home/vivek/index.php ## ##
## But original/actual file remains as it is ##
$ ls -l /webroot/home/httpd/test.com/index.php

Creating Symlink to a directory

The syntax remains same:
$ ln -s
For example, create a symbolic link from the /home/lighttpd/http/users/vivek/php/app/ directory to the /app/ directory you would run:
$ ln -s /home/lighttpd/http/users/vivek/php/app/ /app/
Now I can edit files using /app/
$ cd /app/
$ ls -l
$ vi config.php

How to overwrite symlinks/Soft link

Pass the -f to the ln command to overwrite links:
ln -f -s /path/to/my-cool-file.txt link.txt

How to delete or remove symlinks/soft links

Use the rm command to delete a file including symlinks:
rm my-link-name
unlink /app/
rm /home/vivek/index.php

Getting help about the ln command

Type the following ln command:
$ man ln
$ ln —help

ln command option	Description
—backup	make a backup of each existing destination file
-b	like —backup but does not accept an argument
-d	allow the superuser to attempt to hard link directories (note: will probably fail due to system restrictions, even for the superuser)
-f	remove existing destination files
-i	prompt whether to remove destinations
-L	dereference TARGETs that are symbolic links
-n	treat LINK_NAME as a normal file if it is a symbolic link to a directory
-P	make hard links directly to symbolic links
-r	create symbolic links relative to link location
-s	make symbolic links instead of hard links
-S	override the usual backup suffix
-t	specify the DIRECTORY in which to create the links
-T	treat LINK_NAME as a normal file always
-v	print name of each linked file
—help	display this help and exit
—version	output version information and exit

Conclusion

You learned how to create a symbolic link in Linux using the ln command by passing the -s option. See ln command man page here for more information.

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How to create a hard links in Linux or Unix

How to create a hard links in Linux or Unix

To create a hard links on a Linux or Unix-like system:

1. Create hard link between sfile1file and link1file, run: ln sfile1file link1file
2. To make symbolic links instead of hard links, use: ln -s source link
3. To verify soft or hard links on Linux, run: ls -l source link

Let us see examples to make a hard link on a Linux / Unix systems.

ln command example to make a hard link on a Linux

The ln command make links between files. By default, ln makes hard links.

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ln Command Syntax T Create Hard Link in Linux

The syntax is as follows for Unix / Linux hard link command:

• source is an existing file.
• link is the file to create (a hard link).

To create hard link for foo file, enter:
echo ‘This is a test’ > foo
ln foo bar
ls -li bar foo
Sample outputs:

• 4063240 : Inode. From the above sample output we can see that inodes are identical. We passed the -i option to the ls command to display the index number of each file (inodes).
• 2 : The number of hard links to file is shown in the third column. So if you run, ln foo hlink2 , the counter will increase to three.

How do I delete a hard link on Linux or Unix?

The rm command deletes files on Linux or Unix including a hard link. However, data is still accessible as long as another hard link exists even if you delete source file. To get rid of data you must remove all hard links including source.

Use the rm command:
$ echo ‘I love Linux and Unix’ > file.txt
$ cat file.txt
## create hard links ##
$ ln -v file.txt hardlink1
$ ln -v file.txt hardlink2
## list all files with inodes ##
$ ls -li file.txt hardlink?
## remove 1st hardlink ##
$ rm hardlink1
$ ls -li file.txt hardlink?
## remove source file ##
$ rm file.txt
$ ls -li file.txt hardlink?
## but we can still access original file.txt data ##
$ cat hardlink2
## to get rid of file.txt data delete all hard links too ##
$ rm hardlink2
## error error all data gone ##
$ cat file.txt hardlink?
$ ls -li file.txt hardlink?

Hard Links Limitations on Linux and Unix

There are some issues with hard links that can sometimes make them unsuitable. First of all, because the link is identical to the thing it points to, it becomes difficult to give a command such as “list all the contents of this directory recursively but ignore any links”. Most modern operating systems don’t allow hard links on directories to prevent endless recursion. Another drawback of hard links is that they have to be located within the same file system, and most large systems today consist of multiple file systems.

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