Links are very useful tools for a number of reasons. One very good use of Links is linking to a directory on another drive so you can easily access its contents. Say, for example, you have a hard drive containing mp3 files that is mounted to the directory /data. You want to be able to easily access those mp3 files but you don’t always want to have to navigate through the directory structure to get to them. Make this easy with a link in your ~/ (home) directory.

Types of links

There are two types of links: Hard and Soft (Symbolic) links. The primary difference between hard and soft links is that hard links can only link to a file and can not span drives or volumes. Soft links, however, can link to directories and can span drives/volumes. At first you may think “Why even use hard links?” One major advantage to hard links is that a link will remain even if the original file is moved.

Another difference between hard and soft links, that isn’t really examined by the end user is that hard links reference an exact inode whereas soft links reference abstract files/directories and are given their own, unique inode.

How to create links

Links are created by using the ln command. Hard links are created by using the ln command alone where soft links are created with the ln command using the -s switch.

Let’s start out by creating a hard link. We’ll use a very simple example. Using the Enlightenment E16 window manager requires you to edit the ~/.e16/menus/user_apps file to add to your menu. Let’s say you want a link in your ~/ directory to that file so you’re not always having to type so much to get to that file. You can do this with a hard link by entering the following command (as your standard user:

ln ~/.e16/menus/user_apps ~/user_apps

This will create a link in your home directory called user_apps. The nice thing about this is any time you edit either file, both will change. So you can simply edit the file in your home directory and the changes will reflect in your ~/.e16/menus/user_apps file.

One of the more common uses (as stated earlier) is linking a file from the /usr/lib/mozilla/plugins directory to your ~/.mozilla/firefox/XXX/plugins/ directory. Instead of linking file by file you can just link to the entire directory. NOTE: This is not often the case. Some distributions/installations handle the browser plugin system differently. I am using this as an obvious example of how soft links come in handy.

Where XXX is a random string of characters created upon installation of Firefox.

So to make a soft link from your /usr/lib/mozilla/plugins directory to your ~/.mozilla/firefox/XXX/ directory you would issue the command:

ln -s /usr/lib/mozilla/plugins ~/.mozilla/firefox/XXX/

Now your user installation of Firefox can see the plugins for the global installation. Of course this doesn’t always work in the case of plugins. Again, I state it was used as an obvious example to explains links.

One of the nice aspects of soft links is that a standard user can link to files in any directory. But just because they can link to them doesn’t mean they can edit them. You can create a link from the /etc/hosts.deny file to your home directory but, as the standard user, you can not edit the file. The standard user will, however, see all edits made to this file when edits are made by a user with write permissions.

Confused?

Let me try to explain that in another way. Say, for example, you want your users on your Linux machine to be able to see the contents of file /data/SAMPLE_DATA. You don’t however want them to see the contents of the /data directory. Remove the read permissions from the directory /data with the command:

chmod -R o-w /data

and then give the file SAMPLE_DATA back read permission with:

chmod o+w /data/SAMPLE_DATA

command.

Now link to the SAMPLE_DATA file with the command:

ln /data/SAMPLE_DATA ~/

and the user will have a hard link to the file that they can read but not edit.

Final thoughts

Although links can be a bit confusing, they are a very helpful tool to use with the Linux operating system. They can make your administration job easier and save hard drive space. Get to know links, they are your friends.

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Could be fatal for commercial software that has been bought as it will stop working altogether or revert back to a trial version that is most likely expired. You could uninstall and reinstall the software program. Could be trouble for users who do not have the serial number at hand anymore if the software is commercial. Could also be problematic because of custom settings that will most likely be gone unless they are stored globally.

A quick search on the Internet revealed no free software programs that aid the user in the process. The most popular commercial software program seems to be Application Mover by Funduc which costs $15 for a single user license. We like free here at Ghacks which is why the following way to move applications from one location to another should work as well for you.

Symbolic links come to the rescue. They can be used to point from the original folder to a new folder. Windows will recognize this as one folder in the original location although the files are located on another drive. To move c:\program1 to d:\program1 one would move the contents of c:\program1 to the d drive and create a symbolic link in c:\program1 pointing to the new location.

The process would therefor involve the following steps:

• Move (or copy) the files on c:\program1 to d:\program1
• Create a symbolic link from c:\program1 to d:\program1

There are several programs that can be used to create symbolic links, for example Junction by Sysinternals or SHJunction by Bitsum. The first program is command line driven while the second comes with a graphical user interface.

There is also a Windows Shell Extension for those who prefer to create the symbolic links in Windows Explorer.

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A practical example would be to store files and directories in a different location than they have to reside in. This could be the Firefox profile directory, a Skype directory or the Windows Documents and settings folder. You basically tell Windows to look into the original folder but also in the linked folder for files.

NTFS Link offers three ways of creating hard links and junctions. The first and probably easiest way is by dragging and dropping a file or folder with the right mouse button to another location. The others are by making use of the New parameter in the right-click menu in Windows Explorer while the last works by right-clicking on an empty folder only.

The drag and drop function proves to be really useful and an uncomplicated way of creating hard links and junctions. It should however be noted that NTFS Links works best when run in pre-Vista operating systems as Windows Vista comes with its own possibilities to create symbolic links.

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Users installing the software need to have administrator rights to do so and should note that only NTFS drives support the creation which means that it cannot be used on partitions formatted with FAT file systems. It should also be noted that Link Shell Extension is compatible with 64-bit editions of Windows XP and Windows Vista.

The type of link that is created depends on the source that is picked by the user. Picking files will create hardlinks, folders will create junctions and a partition will create a volume mountpoint. The benefit of creating that file system is that files and folders can be accessed in multiple places instead of just the source location.

In addition to the three link types specified above the Windows Vista version of Link Shell Extension supports the creation of Symbolic Links which have been introduced in the operating system.

The creation of remote links within SMB mapped network NTFS drives is supported by the software program as well. The easiest way to get an overview of the capabilities of Link Shell Extension is to visit the homepage which lists all supported modes and functions.

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