Get to know Linux

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One of the defining features of UNIX is its design philosophy, which emphasizes simplicity, modularity, and the use of small, independent programs that can be combined to perform complex tasks. This approach, known as the "Unix philosophy," encourages the creation of tools that do one thing well and can be combined using shell scripting to achieve more complex functionality.

UNIX provides a multi-user, multi-tasking environment, allowing multiple users to work on the system simultaneously and run multiple programs concurrently. It introduced the concept of hierarchical file systems, where files and directories are organized in a tree-like structure, and everything is treated as a file.

Another key aspect of UNIX is its command-line interface, which allows users to interact with the system using textual commands entered in a terminal. This provides a flexible and efficient way to perform various tasks and automate operations through scripting.

Over the years, UNIX has evolved into different variants or flavors, including the original AT&T UNIX, BSD (Berkeley Software Distribution), and numerous commercial and open-source versions like Linux and macOS (which is based on BSD and NeXTSTEP, a UNIX-like system). These variants have added their own features and modifications while retaining the core principles and compatibility with existing UNIX software.

UNIX has found widespread use in various domains, such as servers, mainframes, supercomputers, embedded systems, and scientific research. It is highly regarded for its stability, security, scalability, and flexibility, making it a preferred choice for many applications and industries.

Overall, UNIX has had a profound influence on the development of operating systems, software engineering practices, and the culture of computing. Its philosophy and principles continue to shape the way modern systems are designed and operated, making it a fundamental part of the history and ongoing development of computing technology.

The GNU project aimed to develop a complete and fully functional operating system composed entirely of free software. Free software refers to software that grants users the freedom to use, study, modify, and distribute it. Stallman believed that software users should have these fundamental freedoms and that proprietary software restricted users' control over their own computers.

The GNU project encompassed a wide range of components, including a kernel, compilers, editors, utilities, and libraries. However, the kernel, called GNU Hurd, initially faced delays in development. To overcome this obstacle and provide a complete system, the GNU project teamed up with the Linux kernel, developed independently by Linus Torvalds, in the early 1990s. This combination of GNU software and the Linux kernel resulted in what is commonly referred to as "GNU/Linux" or simply "Linux."

GNU's contributions to the world of software extend beyond the development of an operating system. The project also developed the GNU General Public License (GPL), a widely used free software license that ensures the freedom of users to modify and distribute software. The GPL has had a profound impact on the open-source software movement and has inspired the creation of many other free and open-source software projects.

The GNU project's philosophy and advocacy for software freedom have played a significant role in shaping the software industry. It has fostered a community of developers dedicated to creating and promoting free software. Numerous GNU tools and utilities, such as the GNU Compiler Collection (GCC), GNU Bash (shell), GNU Emacs (text editor), and many others, are widely used in both GNU/Linux systems and other operating systems.

Overall, the GNU project's mission to develop a free and open-source operating system has had a lasting impact on the software industry, inspiring the creation of numerous free software projects and promoting the ideals of software freedom.

Linux is known for its stability, security, and scalability, and it is used in a wide range of devices and systems, from personal computers to servers, mobile devices, embedded systems, and even supercomputers. Its flexibility and modularity allow it to be adapted to different hardware architectures and customized to suit specific needs.

One of the key features of Linux is its open-source nature. The source code of the Linux kernel and most Linux distributions is freely available, allowing users and developers to study, modify, and distribute it. This fosters a vibrant and collaborative community of developers who contribute to its continuous improvement and development.

The success and popularity of Linux can be attributed to its robustness, security, customizability, and the vibrant open-source community surrounding it. It has become a prominent player in the world of operating systems, serving as the foundation for many technological innovations and powering critical infrastructure across the globe.

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One day, Buddha tested his disciple's mathematical skills with an interesting question in the "THE DIAMOND OF PERFECT WISDOM SUTRA" The sutra stated, "“Subhuti, what do you think? If there were as many Ganges Rivers as the grains of sand in the Ganges, wouldn’t the amount of sand contained in all those Ganges Rivers be great?"

In mathematical terms, it can be translated as, "Subhuti, the quantity of sand in the Ganges River multiplied by the quantity of sand in the Ganges River equals how many grains of sand? Is it many or few?"

Two thousand years later, another deity called "Google" calculated the answer to Buddha's mathematical problem. Upon entering "恆河沙 * 恆河沙" (Ganges River sand multiplied by Ganges River sand) into Google, the answer came out as "1.0 x ¹⁰⁴ "

Google's "divine revelation" of the Ganges River sand quantity being 10⁵² ? The divine revelation is always cryptic and hard to understand. Why isn't it 10⁴⁰ or 10²⁰ ? Well, there's no way to refute it anyway. For humans, both 10²⁰ and 10⁴⁰ are already considered infinite, so 10⁵² is also infinite.

For example, if I owe someone 100 million, 1 billion, or even 10 billion, it's all the same. A dead pig doesn't fear boiling water; in any case, I can't repay it, so I can only shrug and give up.

Returning to Buddha's question, "Ganges River sand quantity multiplied by Ganges River sand quantity" can be mathematically interpreted as ∞ * ∞ = ∞. Therefore, Ganges River sand quantity * Ganges River sand quantity = Ganges River sand quantity (infinity multiplied by infinity still equals infinity). Hence, "沙等恆河沙" (as many Ganges Rivers as the grains of sand in the Ganges is equivalent to "恆河沙" (Ganges River sand).

What does Ganges River sand have to do with Linux? It is often said, "There are no secrets before the source code." Although Linux is touted as open-source, it is full of secrets. Open-source is equivalent to not open-source because the released source code is as numerous as the grains of sand in the Ganges River.

When Torvalds initially released the kernel, it only consisted of about 10,000 lines of source code. However, through the collective efforts of various heroes, its growth can only be described as remarkable. For example, the Kernel version 2.6.12 released in 2005 had nearly 7 million lines of source code, while the version 2.6.30 released four years later surged to over 10 million lines of source code.

The following table shows the versions of the Linux Kernel and the corresponding number of lines of source code:

On January 1, 2020, it was updated that the Linux source code has surged to 27.8 million lines. (Source: https://www.phoronix.com/news/Linux-Git-Stats-EOY2019)"

Regardless of whether Linux's source code consists of 7 million or over 10 million lines, it is infinite to the average person. The source code of Linux, with its vastness comparable to the grains of sand in the Ganges River, represents the ability and complexity of possessing a Ganges River's worth of sand.

In the "First Discourse on Emptiness," faced with the infinite mathematical problem of the "sands of the Ganges," Subhuti's approach would be to embrace the concept of boundless emptiness.

The Chinese philosopher Zhuangzi (莊子) said, "My life has its boundaries, but knowledge has no boundary. To use the limited to pursue the unlimited is perilous. This can also be applied to Linux: "My life has its boundaries, but Linux has no boundary. To use the limited to follow the unlimited is perilous."

Therefore, for those who wish to learn and study Linux, it is impossible to comprehend all its functionalities within one's lifetime. Thus, the attitude towards learning the capabilities and complexities of Linux, which are comparable to a Ganges River's worth of sand, should be to modify "Grains of sand in the Ganges equals the Ganges River"("沙等恆河" 改 "沙等於恆河"). Study and explore the intricacies of a single grain of sand, as it encompasses the understanding of the entire Ganges River. Focus on studying one grain of sand at a time, as each grain of sand represents a world in itself.

Therefore, as a user, you can choose one or two specific areas of interest to begin with. You can start by using Linux to replace Windows for your daily tasks, or delve into understanding Linux network architecture, Shell scripting, or specific principles of the kernel, and so on.

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The poor market share of Linux on PCs compared to Windows may make it seem like learning Linux is not useful. However, in a different arena, Linux can turn the tables.

According to the statistics from the "Top500" list of the world's fastest supercomputers, in 2010, Linux was used as the operating system in 91.8% of the top 500 supercomputers, with the top 30 all running Linux. Windows, on the other hand, only accounted for 3.8% of supercomputers. This reflects the fact that Linux/UNIX is much stronger than Windows in executing critical tasks and in environments that require multitasking and multiple CPUs.

Perhaps supercomputers are too far away from us and not accessible to the average person. However, Linux is right beside you. Currently, the shipment volume of smartphones has exceeded that of PCs, and when it comes to smartphone operating systems, it can be said that Linux/UNIX dominates.

Apple's iPhone operating system, iOS, is actually UNIX-like, and smartphones from hTC/Samsung and others run Android, which directly utilizes the Linux kernel. In this field, Microsoft's Windows Mobile has a pitifully low market share of 7%, while Linux is no longer confined to supercomputers and has made its way into the hands of ordinary people.

The table below shows the market share of smartphone operating systems.

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For those who are accustomed to using Microsoft Windows, they may be familiar with mainstream Windows versions such as XP, Windows 7, and Windows 10. However, when it comes to Linux versions like Redhat, Fedora, Debian, GentOS, Ubuntu, and SUSE, it can be quite confusing.

Talking about UNIX/Linux, it's worth mentioning that the correct term for Linux should be GNU/Linux. It combines the efforts of two major camps, GNU and Linux. However, GNU/Linux, in reality, consists of the kernel, software libraries, and some utility programs. These are like "software components" that only expert hackers can assemble and use. Consequently, many companies, organizations, or individuals have taken on the task of assembling these software components, adding some application software, and releasing them as "Linux distributions".

According to unofficial statistics, there are currently over 200 active Linux distributions. Each distribution has its own specific goals, packaged application software, and user environments. Here are a few commonly seen Linux distributions in the domestic (Taiwanese) market.

• Debian:
  Completely academic atmosphere, not controlled or sponsored by any commercial company, but there are many voluntary developers, adhere to the "Unix style" and "free software spirit" of the two bibles, many distributions on the market are based on Debin.
• Ubuntu:
  It pays great attention to ease of use and turns "Linux into Windows". If you know how to operate Windows, you can get started immediately.
• Redhat/SUSE/GentOS/RockyLinux :
  The target is for enterprise use, with special emphasis on stability, suitable for use as a server (Server) or workstation (Workstation), some versions will charge service fees. ( Last updated : Sep09 2022: "The CentOS team announced on December 8, 2020 that CentOS will only be maintained until the end of 2021 and will not be updated" )
• Fedora/Open SuSE:
  It is a general-purpose distribution, which can be used as a workstation, desktop and server.

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• Bare Metal Installation
  the definition of "empty machine" is "no data on the hard disk is needed". Due to the installation of Linux, it is inevitable that all the data on the hard disk will be deleted due to unfamiliar or careless operation, so please confirm in the learning machine The data on the hard disk has been backed up or is no longer needed .
  
  If you want to use an old PC as a learning machine, plus the PCs in service, the entire table may be occupied by screens and keyboards. At this time, a "KVM switch" can be used to allow two PCs to share peripherals to save investment and space.
  "KVM" is the abbreviation of the three output/input peripherals of Keyboard ,Video, and Mouse. The function of "KVM switch" is to allow two or more PCs to share a set of keyboards and screens . and mouse, the following is the block diagram of the KVM switch.
  
  
  <Picture source http://en.wikipedia.org/wiki/KVM_switch>
  
  Some KVM switches can use the hotkey on the keyboard to freely switch the controlled PC, and the general 3C market should be used in Sell. Take the 2~4 ports used in the learning machine as an example, when purchasing, the keyboard and mouse are divided into USB or PS/2 interface, and the screen is divided into D-SUB/DVI/HDMI/DisplayPort , etc. Don't buy the wrong interface! If you don't know how to choose, you can refer to related products of KVM manufacturer "ATEN" (ATEN) SOHO solution (refer to http://www.aten.com.tw/).
  
• Virtual Machine Installation
  There are many "Virtual Machine" software in the market. The main market of Dell's "VMware" is in the key computing of enterprises, and Oracle's VirtualBox is free and suitable for learning Linux.
  For VirtualBox information and downloads, please refer to the official website: http://www.virtualbox.org/ .
  
  What is a "Virtual Machine"? In fact, this concept existed in ancient China during the Warring States period and was known as "Wuhua",("物化" which translates to "Virtualization to materialization." )
  
  In the book <Zhuangzi>, it is recorded that Zhuangzi once had an experience where he "felt" himself to be a butterfly, happily fluttering and flying. He believed that he was truly a butterfly. However, suddenly he "awoke" and realized that it was just a dream of him being a butterfly. At this point, Zhuangzi was puzzled and questioned himself, "Could it be that I am actually a butterfly who dreamed of being Zhuangzi, and upon awakening, I am still a butterfly, rather than Zhuangzi dreaming of being a butterfly?"
  
  Iit is uncertain whether Zhuangzi", dreamed of being a butterfly or if the butterfly dreamed of being Zhuangzi". The perplexing and intertwined nature of dreams and wakefulness has troubled philosophers and poets for centuries. Zhuangzi referred to this state of being, where reality and illusion seem indistinguishable (perhaps reality seems like an illusion and vice versa), as "物化"(Wuhua)."
  
  Perhaps we may not possess the "Wuhua" supernatural power of Zhuangzi, nor do we have the elegance of the poets who dream of butterflies. However, with the use of a Virtual Machine, the OS on a PC can quickly exhibit the transformative power of "Wuhua." It can virtualize itself into another OS, just like the butterfly in Zhuangzi's dream, blurring the lines between reality and illusion.
  
  Indeed, if you don't have any spare old PC at home, you can still install Linux on your currently operational Windows system using a virtual machine. It's like Windows "dreaming" of being Linux, and the Linux operating system within the dream will behave and function just like a real Linux installation.
  
  Indeed, one of the benefits of using a virtual machine is that you won't risk accidentally formatting your hard drive and losing data while practicing Linux (since it's all within the virtual environment, like a dream). Another advantage is that you can still retain your familiar Windows operating system alongside the virtualized Linux environment. This allows you to switch between the two operating systems seamlessly and use the one you're most comfortable with for different tasks or needs.
  
  In the example you provided, the original operating system, Windows, is referred to as the "Host Operating System" , while the operating system within the dream, Linux, is called the "Guest Operating System" . However, it's worth noting that the roles can be reversed, and Linux can also serve as the host operating system. Regardless of which operating system is the host or guest, the guest operating system is unaware that it has been virtualized and exists within a virtual environment.
  
  Two thousand years later, the Western world also encountered a famous flying creature. Around 1947, in the United States, a vacuum tube computer suddenly crashed. Upon investigation, the technicians discovered that the cause of the computer malfunction was a bug, a moth that had flown into the vacuum tubes, causing a short circuit. This incident marked the first computer bug in history, and appropriately, the term "bug" was used to refer to a problem in a computer system. Additionally, the term "debug" was coined to describe the process of troubleshooting and fixing computer issues, likened to catching and eliminating bugs.
  
  According to my "research," the first computer bug in history occurred in China. During the Warring States period, Zhuangzi used his "physical body" as the hardware of the computer and his brain as the software to experiment with the "virtual machine software." Perhaps he found more joy in transforming into a butterfly, or he realized that he was actually a butterfly. It could also be that Zhuangzi couldn't distinguish whether he was Zhuangzi or a butterfly and experienced a "system crash."
  
  Indeed, both in ancient and modern times, a moth caused system crashes. The difference lies in how Zhuangzi perceived the unintentional intruder, the moth, as part of his "materialization" concept. He believed in the unity of heaven, earth, and himself, stating, "Heaven and earth and I are of the same root; all things and I are of one essence." As everything in the world is interconnected, Zhuangzi didn't rush to catch the moth or "debug" the "beautiful mistake" it caused.
  
  
  The picture below shows the use of VirtualBox to run Linux under Windows.
  
  
  
  
• Utilizing a Hard Drive Enclosure
  If you only have one PC, using the hard disk extraction box is also a good way to use the hard disk extraction box. If you want to use a different operating system, you only need to extract and replace the hard disk of the different operating system, which is quite convenient .
  
  <SATA hard drive enclosure, image source https://www.orico.com.cn>
  

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