The previous article "Environment Preparation and Linux Installation" visually demonstrated the installation of virtual machine software VMware and Centos operating systems. Follow the step-by-step operation of the article, and the installation will be successful. After installing the system, the next step is to log in to the operating system to perform various operations. As the second article in the introductory series, I will briefly introduce the features, graphical user interface (GUI) operation and directory structure of the CentOs operating system.

 

    Before we get started, let's take a look at the Linux operating system and why we chose CentOs as the demo environment for this series of articles.

 

1. Introduction to Linux

1.1 Overview of Linux

    As we all know, the current mainstream operating systems are: Windows, MacOs, Linux. I believe you must be familiar with the Windows operating system developed by Microsoft. Most personal PCs use Windows; MacOs is a Unix kernel-based graphical operating system developed by Apple and runs on Apple series computers; and Linux is a A set of free-to-use and freely disseminated Unix-like operating systems.

    At present, the more well-known distributions on the market are: RedHat, CentOs, Ubuntu, Debian, Fedora, SuSE, OpenSUSE, etc.

    Relatively speaking, because Linux is free and open source, it has a high usage rate in the server market. Note that the commands and operations of different distributions are slightly different. You can choose the corresponding version according to the actual situation. This series of articles uses CentOS7.0 for demonstration.

 

1.2 Differences between Linux and Windows

comparison	Windows	linux
Whether to charge	charge commercial software	open source free
Interface	The interface is unified, and the shortcut keys are almost the same	Different distributions have different interfaces.
Software	Certain functions may require a commercial license	Most software is freely available
Market	Personal PCs are mostly	used for servers

 

1.3 Main Features of Linux

50. open source free
50. Multi-user multi-tasking
50. Everything is a file in Linux
50. The filename does not have a suffix

1.4 Linux version selection

    As mentioned above, there are many distribution versions of Linux: RedHat, CentOs, Ubuntu, Debian, etc. How to choose between the versions?

distribution	Release Description
redhat	RedHat's most well-known linux commercial distribution, with fast version updates and patching, but expensive licensing
centos	CentOs is based on the community edition of Redhat Enterprise Edition and is basically compatible with Redhat. Many network resources and high market share
ubuntu	Ubuntu desktop is very beautiful, simple and gorgeous, if you want to have fun under Linux, Ubuntu is the first choice
debian	Debian is the freest version of all linux distributions. It has many English documents and materials, and it is difficult to get started. Its domestic share has certain limitations.

 

Summarize:

50. First choice for beginners: Centos series

    With a huge user group, 80% of the network resources are based on the CentOs distribution, and it is easy to find solutions when encountering problems; the version can also be easily obtained on the official website or open source sites (such as Alibaba Cloud, 163, etc.); it has a wide range of applications and has Typical and representative, most enterprises are using it, and it is easy to integrate into the actual combat environment of enterprises after learning.

50. Preferred desktop platform: Ubuntu series

    Occupying half of the desktop Linux, it focuses on beautiful desktop, user-friendly operation, good compatibility with hardware, and is the first choice for leisure and entertainment.

50. First choice for enterprise applications: RHEL/Centos series

Enterprise-level pursuit of stability and reliability, if you want to use the RHEL version, you need to purchase commercial authorization and consulting services, RedHat provides system technical support and free upgrades, you can apply for a trial version for a certain period of time. CentOs is a non-commercial distribution and can be downloaded and used for free, but the disadvantage is that it cannot play the latest system patches.

    The choice between the two mainly depends on whether the enterprise has the corresponding technical strength. If it is a line-of-business enterprise that recommends purchasing RHEL, it can save IT management costs and obtain professional technical support; if the enterprise has strong technical strength and has many years of experience in using Linux, Centos releases Edition would be the best option.

    Seeing this, I believe you already know why CentOs was chosen for the demonstration in this article.

2. Basic GUI operation

    What is GUI?

    In fact, you have already seen it, do you still remember the interface you saw after installing the system login in the previous article "Linux Getting Started Series 1--Environment Preparation and Linux Installation", that is GUI: Graphical User Interface (Graphical User Interface)!

2.1 Introduction to CentOs GUI

    The well-known Windows operating system, if it is not for the graphical interface (GUI), will not successfully occupy the high ground of the computer desktop. Although everyone has been complaining about the lack of security and stability of the Windows system, the application and entertainment , Microsoft still wins the favor of most ordinary users, because in their life and work, these are enough.

    The Linux system has always adhered to its own professional line. In the field of server operating systems, with its security and stability, it has always been the absolute main force of enterprises. Most of the people who were familiar with and used linux in the past were concentrated in the community and professionals, but this situation is constantly changing, and everyone realizes that they cannot be limited to one product at any time, otherwise there is a danger of being dominated by individuals and enterprises. . At the same time, the linux system itself is constantly improving its graphical interface products, and more and more users turn to linux.

    Although many applications and entertainment are still unavailable under some linux (settings include some drivers), this situation has gradually improved. Therefore, this series of articles deliberately released the GUI part in advance for your reference.

    The mainstream environments in the Linux desktop system are: GNOME, KDE, and Xfce, LXDE, etc. have also been widely used.

    When installing CentOs in the previous article, I chose "Server with GUI", and the default installed interface environment is GNOME.

 

It can also be seen from the above figure that CentOs provides GNOME and KDE options by default

 

 

2.2 GUI Basic Operation

2.2.1 Start the virtual machine and log in to the CentOs system

    Start the VMware software and click the "Power On This Virtual Machine" button in the image below

 

    Waiting quietly for the login screen to appear

    You can click the "Not listed" button to switch the user who needs to log in. This article switches to root login

 

 

    In the input interface, click the icon next to login, you can see that the GUI adopts the "GHOME Classic" classic mode by default

 

 

Enter the password and click "next"

 

2.2.2 Check the network connection

    Since the FireFox browser already comes with it, the most direct way is to browse the web page to see if you can access the Internet.

 

After the installation of the previous article, the NAT mode is selected and the IP address is set, so the Internet can be accessed directly.

ps: If the IP is not set or the settings are incorrect during installation, you cannot directly access the Internet at this time. You can set it as follows.

 

 

 

    You can configure the IP and gateway according to your local network conditions. The configuration method is the same as the previous article. If you forget, you can read the previous article.

 

2.2.3 Right-click menu

    Right-click the mouse on the desktop to pop up the right-click menu

 

    You can create a new folder (New Folder), open a terminal (Open in Terminal), modify the desktop background (Change Desktop Background) and so on.

    The operation is relatively simple and will not be demonstrated one by one.

 

2.2.4 Common applications

    Click the "Applications" application button (equivalent to the start menu of the windows system) to pop up all installed applications

 

2.2.5 File Directory

    Click "Places" to quickly index to the corresponding file directory, which is equivalent to "My Computer" in the Windows system

 

2.2.6 System Settings

    Click the login user icon in the upper right corner of the system, select "Settings" in the pop-up box, and you can perform various system settings in the newly popped up Settings window. Equivalent to the Windows "System Settings" or "Control Panel" function

 

 

2.2.7 Logout, Shutdown and Restart

    Click the login user icon in the upper right corner of the system, and you can log out (LogOut), lock (Lock), and shut down (Power Off) operations in the pop-up box. Insert picture description here So far, the basic operation of Centos GUI is introduced.

    Due to space limitations, how to perform service management, system settings, software download and installation under the GUI will not be discussed, and it is not the main content of this series of articles. If necessary, you can consult the relevant information.

 

3. CentOs directory structure

    As mentioned earlier, everything in the Linux system is a file, so how are the files organized?

 

3.1 Intuitively understand the directory structure of CentOs

    Click the "Places" button and select "Computer", which is equivalent to "My Computer" under Windows

 

 

 

    If you are careful, you may find that the directory structure of Linux is very different from that of windows. Unlike windows, which has many drive letters such as C, D, and E, she has only one root directory, forming a tree structure.

 

    The directory structure is like a tree (the picture is excerpted from the Internet)

 

 

3.2 目录介绍

Directory	Purpose
bin	The directory of executable binary files, which stores commonly used commands such as ls, tar, mv, cat, etc.
boot	Put the core files used when the linux system starts, and don't put your own installation here. A separate partition is recommended, and the partition size is 100M.
dev	Store device files under the linux system, and accessing a file in this directory is equivalent to accessing a device
etc	The directory where the system configuration files are stored. It is not recommended to store executable files in this directory.
home	Stores the home directory of ordinary users. When adding a user account, the user's home directory is stored in this directory. It is recommended to partition separately and set a larger disk space to facilitate users to store data
lib	The directory of the function library used by the system
mnt	The directory mount directory of the function library used by the system, temporarily mount other file systems, such as mounting the CD-ROM to /mnt/, you can enter the directory to view the contents of the CD-ROM
opt	The directory where additional software is installed on the host. For example, if you install the oracle database, you can put this directory down. It is empty by default. In the previous Linux system, it was accustomed to be placed in the /usr/local directory
proc	The virtual directory is the mapping of system memory, and you can directly access this directory to obtain system information. Since the data is stored in memory, it does not occupy disk space
root	The home directory of the system administrator root, the first partition of the system to start is /, so it is best to place /root and / in one partition
run	should be deleted or cleared. If you have a /var/run directory on your system, it should point to run
sbin	s stands for Super User, where the executable commands used by the system administrator, such as fdisk, shutdown, mount, etc., are placed. Different from /bin, these directories are commands used by the system administrator root, and ordinary users can only "view" but cannot set and use them.
srv	Service Abbreviation, the data directory that needs to be accessed after the service is started
sys	This is a big change from the linux2.6 kernel. A new file system sysfs in the 2.6 kernel is installed in this directory
tmp	directory for temporary files
usr	Application storage directory, similar to the program files directory under windows, it is recommended to partition separately and set a larger disk space
var	Place files that change frequently during system execution, such as log files that change at any time. It is recommended to partition separately and set a larger disk space

    So far, the basic operations and directory structure of the Centos graphical interface have been introduced. Now we can do some routine operations on the local Centos system, but if it is a server, we cannot go to the computer room every time. Therefore, the next article will explain Knowledge of remote login.

 

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