009 Create Hard and Soft Links

Tech Tutorial: Understand and Use Essential Tools #

Introduction #

In the Red Hat Certified System Administrator (RHCSA) exam, one of the essential skills you’ll need is the ability to create and manage hard and soft links within the file system. This tutorial aims to explain what hard and soft links are, why they are used, and how you can create and manage them in a Red Hat Enterprise Linux (RHEL) environment.

Before diving into the commands, let’s understand what hard and soft links are:

  • Hard Links: A hard link is essentially an additional name for an existing file on the same filesystem. It is an entry in a directory that associates a name with a file on a disk. Notably, a hard link cannot reference directories and cannot cross filesystem boundaries.

  • Soft Links (Symbolic Links): A soft link, or a symbolic link, is a special type of file that serves as a reference, or a pointer, to another file or directory. Unlike a hard link, a symbolic link can point to a file or a directory across filesystem boundaries.

Step-by-Step Guide #

To create a hard link in RHEL, you use the ln command without any options. Here’s how you do it:

Syntax: #

ln [source file] [hard link]

Detailed Code Example: #

Suppose you have a file named original.txt and you want to create a hard link named hardlink.txt to this file:

touch original.txt  # Creates the original file
ln original.txt hardlink.txt  # Creates a hard link to original.txt
ls -li original.txt hardlink.txt  # Lists the files showing inode information

In the above example, both original.txt and hardlink.txt will share the same inode number, indicating that they are truly just two names for the same file content.

Creating soft links, or symbolic links, is done using the ln command with the -s option.

Syntax: #

ln -s [target file/directory] [symbolic link]

Detailed Code Example: #

If you want to create a symbolic link named symlink.txt that points to original.txt:

ln -s original.txt symlink.txt  # Creates a symbolic link to original.txt
ls -li original.txt symlink.txt  # Lists the files showing inode information

In this example, symlink.txt will have a different inode number and will point to original.txt. If original.txt is moved or deleted, the symbolic link will break and will not resolve to a file.

To view files and understand their links, you can use ls -l which will show you detailed information about the files, including their links.

Example:

ls -l

This will display the number of links, permissions, owner, group, size, and timestamp of each file, along with link directions for symbolic links.

Conclusion #

Understanding and managing hard and soft links is a fundamental skill for any system administrator, especially for those preparing for the RHCSA exam. Hard links allow you to have multiple filenames associated with the same file content, which can be useful for backup and recovery strategies. Soft links, meanwhile, offer a flexible way of creating pointers to files and directories, potentially across different filesystems. Mastery of these concepts and commands ensures efficient file management and organization in a Linux environment.

Remember, practice is key to mastering these commands, so consider setting up various scenarios on your own RHEL system to test out these concepts.