Understanding File Systems in Linux: Hard Links, Soft Links, and Beyond
Simplify file organization with a clear understanding of link types in Linux.
In the Linux world, understanding the file system is a cornerstone of effective system management. Beyond the basics of directories and files lies the powerful concept of links—a way to access and manage data efficiently without duplicating it.
This article dives into two essential types of links: hard links and soft links (or symbolic links). Both serve unique purposes and can make your work in Linux significantly more streamlined when used correctly.
Whether you’re curious about how links differ, why they matter, or how to use them, this guide will break it all down for you in a simple and practical way. Let’s explore the foundations of Linux file systems and unlock the potential of hard and soft links!
- There are 7 types of files in Linux:
Regular files (-):- The most common type of file, containing data, text or programming instructions.
Directory files (-d):- Also known as folder, these files organize other files and directories.
Symbolic Links (-l):- Also known as link files, these are pointers to other files.
FIFO special (-p):- Used for Inter-process communication (IPC), allowing data to be passed.
Block Device files (-b):- Represent hardware device that read/write data in blocks, such as hard drives.
Character Device files (-c):- Represents device that transmits data character by character, such as keywords, mice or serial numbers.
Socket files (-s):- Enable communication between process over a network or within the same machine. Commonly for client-server communication.
- Hard Link vs Soft Links.
—> Hard Link
A hard link is essentially an additional name for a file.
Both the original file and the hard link shar the same “inode number“ and point to the same physical data on disk.
Changes made to one reflect in the other.
Key characteristics of Hard Links:
Shares the same inode number and file data as the original file.
Cannot link to directories (for safety reasons)
If the original file is deleted, the hard link remains functional because it still reference the same file.
Hard links can only exist within same filesystem.
For creating a hard link:
# ln original_file hard_link
eg - ln file.txt hard_link
For checking inode numbers:
# ls -li
—> Soft Link (Symbolic Link)
A soft link (or symbolic link) is a pointer to the original file path, not its inode. It acts like a shortcut unlike hard links, soft links can point to the directories and cross different filesystem.
However, if the original file is deleted, the soft link becomes broken (a ‘dangling link‘) because it points non-existing path.
Key characteristics of soft link:
Different inode from the original file.
Can link to files or directories.
If the target file is deleted, the soft link becomes non-functional.
Creating a soft link:
# ln -s /path/to/original_file soft_link
eg - # ls -s file.txt soft_link.txt
For changing symbolic links:
# ls -l
| Comparison Parameters | Hard link | Soft link |
| Inode number | Files that are hard linked take the same inode number. | Files that are soft linked take a different inode number. |
| Directories | Hard links are not allowed for directories. (Only a superuser* can do it) | Soft links can be used for linking directories. |
| File system | It cannot be used across file systems. | It can be used across file systems. |
| Data | Data present in the original file will still be available in the hard links. | Soft links only point to the file name, it does not retain data of the file. |
| Original file’s deletion | If the original file is removed, the link will still work as it accesses the data the original was having access to. | If the original file is removed, the link will not work as it doesn’t access the original file’s data. |
| Speed | Hard links are comparatively faster. | Soft links are comparatively slower. |
Q. What is glibc?
Answer=> GNU C library (glibc), is the standard C library used by Linux distributions. It provides the core libraries for the C programming language, including:
File handling
Memory management
String manipulation
Networking
Multithreading
* Key Points:-
Core components:- Most Linux application depend on glibc since it provides the functional interface between the program and the Linux Kernel.
Binary Compatibility:- Ensures programs can run on different Linux distribution, by offering a consistent API.
Widely Used:- It is used by various programming languages, not just C, eg - Python, Java and Ruby indirectly rely on it.
* Process Execution -
Process Creation :
A new process is created using system calls like fork().
Process Scheduling :
Linux uses a schedular to allocate CPU time to process.
Processes are assigned different priorities and can run in various scheduling policies. (eg - real time).
Process States :
A process in Linux can be in one of the following states :
Running : Actively executing on the CPU.
Waiting : Waiting for resources or I/O to complete.
Stopped : Suspended, usually by a signal.
Zombie : Terminated, but its information is still available for the parent to read.
Inter-Process Communication (IPC) :
Process can communicate with each other using mechanism like pipes, signals, shared memory or message queue.
Process Termination :
A process can terminate normally or terminated by a signal.
When a process terminates, it became a “zombie“ until the parent process reads its exit status.
Process Control :
Commands like ps, top and htop are used to monitor process.
Tools like kill, nice, and renice help control or modify process behavior.
Understanding how Linux handles files and links is a crucial step for anyone diving deeper into system administration or software development. Hard links and soft links offer efficient ways to manage data, improve file access, and avoid redundancy in your file system.
While hard links are great for creating additional access points within the same filesystem, soft links shine when it comes to flexibility across directories and devices. Knowing when and how to use these tools can save time and optimize your workflow.
By mastering these concepts, you not only enhance your Linux skills but also gain a deeper appreciation for how file systems operate under the hood. So, go ahead—experiment with links, explore their use cases, and take your Linux expertise to the next level!
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