Features of red hat linux: 1. Multi-user and multi-task operating system, one computer can be used by multiple users at the same time, and can execute multiple tasks submitted by multiple users at the same time; 2. Good Compatibility; 3. Powerful portability, whether it is a handheld computer, a personal computer, a small computer, a medium-sized computer, or even a large computer can run Linux; 4. High stability, reliability and security; 5 , openness and low cost.

#The operating environment of this tutorial: Red Hat Enterprise Linux 6.1 system, Dell G3 computer.

Introduction to red hat linux

What is red hat linux

Red Hat Linux ((RHEL)) is developed by Red An open source Linux distribution compiled by Hat Company. It was active from 1995 to 2004, with several versions of the software released during this period.

Various versions of Red Hat Linux have been released, with the first version released on May 13, 1995. Red Hat Linux was created to be easy to use and install compared to other Linux distributions . It included a graphical installer that was later used by other Linux distributions. Later versions included UTF-8 encoding, making it more suitable for a wider range of languages. However, due to copyright and patent issues, Red Hat Linux lacks many features, such as support for the NTFS file system and MP3, but these features can be installed later.

In 2003, Red Hat Linux merged with the community-based Fedora project, which replaced the original retail and download versions of Red Hat Linux.

Red Hat Linux (RHEL) is a Linux-based operating system designed by Red Hat specifically for enterprises. RHEL can run on a desktop, server, hypervisor, or cloud. Red Hat is one of the most widely used Linux distributions in the world.

RedHat is an operating system based on LINUX core architecture. RedHat Linux is currently the most used Linux operating system in the world. Because it has the best graphical interface, it is very convenient to install, configure and use, and it runs stably, so both novices and experienced players speak highly of it.

Characteristics of red hat linux

1. Multi-user multi-tasking operating system

refers to a A computer can be used by multiple users at the same time and can perform multiple tasks submitted by multiple users at the same time.

• Multi-user: Linux supports multiple users using the same computer from the same or different terminals at the same time, without the so-called license restrictions of commercial software;

  Linux treats different types of users differently, granting them different permissions and storage spaces respectively. Each user has specific permissions to use their own software and hardware resources (such as files and devices), which are independent of each other and do not affect each other. .

• Multi-tasking: Within the same time period, Linux can respond to different operation requests from multiple users.

2. Good compatibility

Complies with IEEE's POSIX (Portable Operating System Interface of UNIX, Portable Operating System Interface for UNIX) standard and is compatible with current mainstream UNIX system. Programs that can run in UNIX can almost entirely run in Linux, which makes it possible to transfer application systems from UNIX to Linux.

3. Powerful portability

Whether it is a handheld computer, a personal computer, a small computer, a medium-sized computer, or even a large computer, Linux can be run.

4. High stability, reliability and security

Linux inherits the excellence of UNIX and can run continuously for months or years without restarting.

So far, only a handful of viruses have infected Linux. This strong immunity is attributed to Linux’s robust infrastructure.

Linux's infrastructure consists of multiple layers that have nothing to do with each other. Each layer has specific functions and strict permissions to ensure maximum stable operation.

5. Openness and low fees.

Red Hat Redhat—Linux basic command line usage

1. What is a shell?

bash shell

A command line is a text-based interface that can be used to enter instructions into a computer system; the linux command line is provided by a program , this program is called a shell.

#What is a shell prompt?

Use the shell interactively and display a string while waiting for the user to enter a command. This interface is called a prompt.

When ordinary users start the shell, the interface ends with a dollar and a $ character.

When the root user starts the shell, the interface ends with the # character.

[root@localhost?~]#

When ordinary users start the shell, the interface ends with the $ character.

[user@localhost?~]$

對(duì)Linux系統(tǒng)的管理方式可以通過(guò)物理控制臺(tái)和虛擬控制臺(tái)管理物理控制臺(tái)就是使用鍵盤(pán)鼠標(biāo)和顯示器對(duì)Linux系統(tǒng)進(jìn)行管理，或者通過(guò)串行端口管理。

虛擬控制臺(tái)是通過(guò)網(wǎng)絡(luò)或者其它虛擬控制方式管理Linux系統(tǒng)。

RHEL8.0的版本同時(shí)提供6個(gè)控制臺(tái)管理，第一個(gè)控制臺(tái)為圖形化管理也叫GUI管理，另外二至六控制臺(tái)為命令行管理方式；可以通過(guò)按住Ctrl+Alt并按住功能鍵（F2-~F6）切換。

二、基本命令

1.命令訪問(wèn)

標(biāo)準(zhǔn)Linux命令行語(yǔ)法格式：command + -option + argument。
command （命令字）：運(yùn)行程序的名字，永遠(yuǎn)寫(xiě)在開(kāi)頭。
option （選項(xiàng)）：由一個(gè)或兩個(gè)“-”引導(dǎo)，改變命令的行為。
argument（參數(shù)）：通常是命令要操作的目標(biāo)，注意先后順序，大多數(shù)命令可以使用--help 顯示用法信息。
大多數(shù)參數(shù)一般可以與選項(xiàng)顛倒使用，不需要刻意規(guī)定（不是所有）。

[root@localhost ~]# ls -l /etc/passwd
-rw-r--r--. 1 root root 2658 12月  9 14:56 /etc/passwd

#命令（ls）、 選項(xiàng)（-l）、參數(shù)（/etc/passwd）
命令、選項(xiàng)、參數(shù) 之間都必須要使用空格隔開(kāi)。
選項(xiàng)： 用于修飾或者調(diào)整命令，不同選項(xiàng)會(huì)使命令有不同的作用。
短選項(xiàng)：-
長(zhǎng)選項(xiàng)：--
可以同時(shí)跟多個(gè)選項(xiàng)，比如 --l --h = --lh

2.參數(shù)：命令的作用對(duì)象

注：

ls -a ls--all

一個(gè)“-”后面跟簡(jiǎn)寫(xiě) 。 兩個(gè)“--”后面跟全稱(chēng)

[root@localhost ~]# usermod -L rhel

#命令（usermod） 選項(xiàng)（-L） 和參數(shù)（rhel）
該命令的意思是鎖定用戶user帳戶的密碼。
exit或ctrl + d退出當(dāng)前shell

3.配置主機(jī)名

[root@localhost ~]# hostnamectl set-hostname server
[root@localhost ~]# bash
[root@server ~]#

exit退出再次登錄shell或者bash

4.修改系統(tǒng)語(yǔ)言

[root@server ~]# locale //查看系統(tǒng)語(yǔ)言包
LANG=zh_CN.UTF-8
LC_CTYPE="zh_CN.UTF-8"
LC_NUMERIC="zh_CN.UTF-8"
LC_TIME="zh_CN.UTF-8"
LC_COLLATE="zh_CN.UTF-8"
LC_MONETARY="zh_CN.UTF-8"
LC_MESSAGES="zh_CN.UTF-8"
LC_PAPER="zh_CN.UTF-8"
LC_NAME="zh_CN.UTF-8"
LC_ADDRESS="zh_CN.UTF-8"
LC_TELEPHONE="zh_CN.UTF-8"
LC_MEASUREMENT="zh_CN.UTF-8"
LC_IDENTIFICATION="zh_CN.UTF-8"
LC_ALL=
[root@server ~]# localectl set-locale.UTF-8 //英語(yǔ)
[root@server ~]# reboot //重啟系統(tǒng)

更改語(yǔ)言后要重啟系統(tǒng)才能生效,GUI登陸時(shí)會(huì)有更改家目錄文件夾名字的彈窗點(diǎn)擊Update Names。

[root@server ~]# localectl set-locale LANG=zh_CN.UTF-8 簡(jiǎn)體中文
在Linux系統(tǒng)中，命令是嚴(yán)格區(qū)分大小寫(xiě)的（謹(jǐn)記）。
系統(tǒng)語(yǔ)言問(wèn)題:

[root@server ~]# echo $LANG		//顯示目前所支持的語(yǔ)言
en_US.UTF-8

zh_CN.UTF-8 簡(jiǎn)體中文
en_US.UTF-8 英文

5.用戶名密碼管理：

[root@server ~]# useradd rhel1		//創(chuàng)建rhel1用戶
[root@server ~]# passwd rhel1 		//后面跟的是用戶名
Changing password for user rhel1.
New password: 		//此處為輸入的密碼，不顯示位數(shù)
BAD PASSWORD: The password is shorter than 8 characters
Retype new password: 		//此處為輸入的密碼，不顯示位數(shù)
passwd: all authentication tokens updated successfully.

創(chuàng)建一個(gè)用戶名為rhel1 密碼為redhat
或者：

[root@server ~]# echo "redhat" | passwd --stdin rhel1		//可以看見(jiàn)密碼

對(duì)在線處理用戶的鎖定及管理操作

[root@server ~]# who		//查看當(dāng)前在線用戶
root     pts/0        2020-12-14 18:18 (192.168.2.108)
root     tty2         2020-12-14 18:34 (tty2)
rhel     tty3         2020-12-14 18:35 (tty3)
[root@server ~]# pkill -19 -t tty3		//鎖定tty3用戶
[root@server ~]# pkill -18 -t tty3		//釋放tty3用戶

6.cat

cat [選項(xiàng)] [文件]或絕對(duì)路徑

cat主要有三大功能：

1）一次顯示整個(gè)文件:cat /etc/passwd

[root@server ~]# cat /etc/passwd		//顯示整個(gè)passwd文件
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
……
rhel:x:1000:1000:rhel:/home/rhel:/bin/bash
rhel1:x:1001:1001::/home/rhel1:/bin/bash

2）從鍵盤(pán)創(chuàng)建一個(gè)文件:cat > filename 只能創(chuàng)建新文件,不能編輯已有文件。

[root@server ~]# cat > filename

3）將幾個(gè)文件合并為一個(gè)文件:cat file1 file2 > file3

[root@server ~]# touch file1 file2 file3		//創(chuàng)建file1 file2 file3
[root@server ~]# vim file1 		//i編輯hello1 按esc ：wq保存退出
[root@server ~]# vim file2		//i編輯hello1 按esc ：wq保存退出
[root@server ~]# cat file1 file2 > file3		//把file1 file2文件的內(nèi)容輸入到file3
[root@server ~]# cat file3		//查看file3文件
hello1
hello2

7.rm 刪除文件命令

rm --f 文件名 [將會(huì)強(qiáng)行刪除文件，且無(wú)提示]

rm --rf 目錄名字 [刪除文件夾以及文件夾中的所有文件命令]

其中：

• --r：向下遞歸刪除

• --f：直接強(qiáng)行刪除，且沒(méi)有任何提示

注意：
使用rm --rf要格外注意，linux中沒(méi)有回收站，慎重操作。

8.時(shí)間管理

[root@server ~]# date		//查看當(dāng)前用戶的年月日星期時(shí)間
Mon Dec 14 19:24:30 CST 2020
[root@server ~]# date +%R		//查看當(dāng)前用戶時(shí)間
19:24
[root@server ~]# date +%x		//查看當(dāng)前用戶年月日
12/14/2020
[root@server ~]# date -s 20201215		//修改時(shí)間為2020年12月15日
Tue Dec 15 00:00:00 CST 2020
[root@server ~]# date -s 20:20:20		//修改時(shí)間為20點(diǎn)20分20秒
Tue Dec 15 20:20:20 CST 20

--s 修改時(shí)間

• date +%Y.%m.%d （Y大寫(xiě)，m、d小寫(xiě)）

• date +%H：%M：%S （大寫(xiě)）

[root@server ~]# cal		//直接執(zhí)行，顯示系統(tǒng)當(dāng)月的日歷
    December 2020   
Su Mo Tu We Th Fr Sa
       1  2  3  4  5
 6  7  8  9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31

[root@server ~]# cal 2020		//顯示2020年整個(gè)年度的日歷
                               2020                               

       January               February                 March       
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
          1  2  3  4                      1    1  2  3  4  5  6  7
 5  6  7  8  9 10 11    2  3  4  5  6  7  8    8  9 10 11 12 13 14
12 13 14 15 16 17 18    9 10 11 12 13 14 15   15 16 17 18 19 20 21
19 20 21 22 23 24 25   16 17 18 19 20 21 22   22 23 24 25 26 27 28
26 27 28 29 30 31      23 24 25 26 27 28 29   29 30 31            
                                                                  
        April                   May                   June        
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
          1  2  3  4                   1  2       1  2  3  4  5  6
 5  6  7  8  9 10 11    3  4  5  6  7  8  9    7  8  9 10 11 12 13
12 13 14 15 16 17 18   10 11 12 13 14 15 16   14 15 16 17 18 19 20
19 20 21 22 23 24 25   17 18 19 20 21 22 23   21 22 23 24 25 26 27
26 27 28 29 30         24 25 26 27 28 29 30   28 29 30            
                       31                                         
        July                  August                September     
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
          1  2  3  4                      1          1  2  3  4  5
 5  6  7  8  9 10 11    2  3  4  5  6  7  8    6  7  8  9 10 11 12
12 13 14 15 16 17 18    9 10 11 12 13 14 15   13 14 15 16 17 18 19
19 20 21 22 23 24 25   16 17 18 19 20 21 22   20 21 22 23 24 25 26
26 27 28 29 30 31      23 24 25 26 27 28 29   27 28 29 30         
                       30 31                                      
       October               November               December      
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
             1  2  3    1  2  3  4  5  6  7          1  2  3  4  5
 4  5  6  7  8  9 10    8  9 10 11 12 13 14    6  7  8  9 10 11 12
11 12 13 14 15 16 17   15 16 17 18 19 20 21   13 14 15 16 17 18 19
18 19 20 21 22 23 24   22 23 24 25 26 27 28   20 21 22 23 24 25 26
25 26 27 28 29 30 31   29 30                  27 28 29 30 31

[root@server ~]# cal 12 2020		//顯示2020年12月份的日歷
    December 2020   
Su Mo Tu We Th Fr Sa
       1  2  3  4  5
 6  7  8  9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31

9.bc 計(jì)算器

bc [回車(chē)]
scale=3 顯示小數(shù)點(diǎn)后面三位
quit 退出

10.cd切換目錄

cd - 退回到當(dāng)前用戶家目錄
cd a/b/c 相對(duì)路徑：以當(dāng)前目錄作為起點(diǎn)，切換目錄 *
cd /root/a/b/c 絕對(duì)路徑：以根目錄作為起點(diǎn)，切換目錄
cd .. 返回上一級(jí)目錄
cd ~ 退回當(dāng)前用戶的家目錄

11.正確的關(guān)機(jī)方法：

[root@server ~]# reboot		//重啟主機(jī)

其它一些關(guān)機(jī)命令：halt、poweroff

shutdown的一些參數(shù)使用：

shutdown [-t seconds] [-arkhncfF] Time [warning message]

-t sec: Add the number of seconds after -t, which is how many seconds have passed The meaning of shutting down after seconds

Parameters:

• -k: Don’t actually shut down, just send a warning message

• -r: Restart the system after stopping the service

• -h: Stop the system service Shut down after shutdown

• -n: Shut down directly using the shutdown function without going through the init program

• -f: After shutdown, force the disk check of fsck to be skipped

• -F: After restart, force the disk check of fsck to be performed

• -c: Cancel the content of the shutdown command that is already in progress.

Time: This refers to the time when the system is shut down.

Example:

/sbin/shutdown -h 10 "I will shutdown after 10 mins"
Let me tell you that this machine will shut down after 10 minutes. And send this warning message to everyone's screen

init: service level, there are 7 levels in Linux, now let's learn about the 4 commonly used levels

• init 0 Shutdown

• init 3 Pure command line mode

• init 5 Mode with graphical interface

• init 6 Restart

What is the difference between shutdown and halt?

shutdown is to gradually shut down the services that have been started before performing a hardware shutdown. Halt does not consider what service is currently started and directly shuts down the hardware.

12. Commonly used shortcut keys under Linux

tab: Complete command or path
ctrl c: Terminate the currently executed Task
ctrl l: Clear the screen
ctrl d: exit
ctrl u: Delete the content with the cursor to the beginning of the line
ctrl e: Move the cursor to the end of the line
ctrl a: Move the cursor to the beginning of the line
ctrl plus sign/minus sign: adjust the shell window font size

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