What are the characteristics of red hat linux

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. tasks; 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 and reliability sex and safety; 5. openness and low cost.

Introduction to red hat linux

What is red hat linux

Red Hat Linux (RHEL) is a Linux distribution compiled by Red Hat company in an open-source manner. It actively released several software versions between 1995 and 2004.

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's Linux-based operating system designed specifically for enterprises refers to Red Hat Linux (RHEL). 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. Currently, the most widely used Linux operating system in the world is RedHat Linux. 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 to a computer system; the Linux command line is provided by a program, which 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 ~]$

The management method of the Linux system can be managed through the physical console and virtual console. The physical console is to use the keyboard, mouse and monitor to manage the Linux system, or through the serial Perform port management.

虚拟控制台是通过网络或者其它虚拟控制方式管理Linux系统。

RHEL8.0的版本同时提供6个控制台管理，第一个控制台为图形化管理也叫GUI管理，另外二至六控制台为命令行管理方式；可以通过按住Ctrl+Alt并按住功能键（F2­~F6）切换。

二、基本命令

1.命令访问

标准Linux命令行语法格式：command + -option + argument。
command （命令字）：运行程序的名字，永远写在开头。
option （选项）：由一个或两个“-”引导，改变命令的行为。
argument（参数）：通常是命令要操作的目标，注意先后顺序，大多数命令可以使用--help 显示用法信息。
大多数参数一般可以与选项颠倒使用，不需要刻意规定（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）、 选项（­l）、参数（/etc/passwd）
命令、选项、参数 之间都必须要使用空格隔开。
选项： 用于修饰或者调整命令，不同选项会使命令有不同的作用。
短选项：-
长选项：--
可以同时跟多个选项，比如 -­l -­h = -­lh

2.参数：命令的作用对象

注：

ls -a ls--all

一个“-”后面跟简写 。 两个“--”后面跟全称

[root@localhost ~]# usermod -L rhel

#命令（usermod） 选项（­L） 和参数（rhel）
该命令的意思是锁定用户user帐户的密码。
exit或ctrl + d退出当前shell

3.配置主机名

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

exit退出再次登录shell或者bash

4.修改系统语言

[root@server ~]# locale //查看系统语言包
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 //英语
[root@server ~]# reboot //重启系统

更改语言后要重启系统才能生效,GUI登陆时会有更改家目录文件夹名字的弹窗点击Update Names。

[root@server ~]# localectl set-locale LANG=zh_CN.UTF-8 简体中文
在Linux系统中，命令是严格区分大小写的（谨记）。
系统语言问题:

[root@server ~]# echo $LANG		//显示目前所支持的语言
en_US.UTF-8

zh_CN.UTF­8 简体中文
en_US.UTF­8 英文

5.用户名密码管理：

[root@server ~]# useradd rhel1		//创建rhel1用户
[root@server ~]# passwd rhel1 		//后面跟的是用户名
Changing password for user rhel1.
New password: 		//此处为输入的密码，不显示位数
BAD PASSWORD: The password is shorter than 8 characters
Retype new password: 		//此处为输入的密码，不显示位数
passwd: all authentication tokens updated successfully.

创建一个用户名为rhel1 密码为redhat
或者：

[root@server ~]# echo "redhat" | passwd --stdin rhel1		//可以看见密码

对在线处理用户的锁定及管理操作

[root@server ~]# who		//查看当前在线用户
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		//锁定tty3用户
[root@server ~]# pkill -18 -t tty3		//释放tty3用户

6.cat

cat [选项] [文件]或绝对路径

cat主要有三大功能：

1）一次显示整个文件:cat /etc/passwd

[root@server ~]# cat /etc/passwd		//显示整个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）从键盘创建一个文件:cat > filename 只能创建新文件,不能编辑已有文件。

[root@server ~]# cat > filename

3）将几个文件合并为一个文件:cat file1 file2 > file3

[root@server ~]# touch file1 file2 file3		//创建file1 file2 file3
[root@server ~]# vim file1 		//i编辑hello1 按esc ：wq保存退出
[root@server ~]# vim file2		//i编辑hello1 按esc ：wq保存退出
[root@server ~]# cat file1 file2 > file3		//把file1 file2文件的内容输入到file3
[root@server ~]# cat file3		//查看file3文件
hello1
hello2

7.rm 删除文件命令

rm ­-f 文件名 [将会强行删除文件，且无提示]

rm ­-rf 目录名字 [删除文件夹以及文件夹中的所有文件命令]

其中：

• -­r：向下递归删除

• -­f：直接强行删除，且没有任何提示

注意：
使用rm -­rf要格外注意，linux中没有回收站，慎重操作。

8.时间管理

[root@server ~]# date		//查看当前用户的年月日星期时间
Mon Dec 14 19:24:30 CST 2020
[root@server ~]# date +%R		//查看当前用户时间
19:24
[root@server ~]# date +%x		//查看当前用户年月日
12/14/2020
[root@server ~]# date -s 20201215		//修改时间为2020年12月15日
Tue Dec 15 00:00:00 CST 2020
[root@server ~]# date -s 20:20:20		//修改时间为20点20分20秒
Tue Dec 15 20:20:20 CST 20

-­s 修改时间

• date +%Y.%m.%d （Y大写，m、d小写）

• date +%H：%M：%S （大写）

[root@server ~]# cal		//直接执行，显示系统当月的日历
    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

<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">[root@server ~]# cal 2020 //显示2020年整个年度的日历 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</pre><div class="contentsignin">Copy after login</div></div><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">[root@server ~]# cal 12 2020 //显示2020年12月份的日历 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</pre><div class="contentsignin">Copy after login</div></div><p><strong>9.bc 计算器</strong></p><p><code>bc [回车]
scale=3 显示小数点后面三位
quit 退出

10.cd切换目录

cd ­ 退回到当前用户家目录
cd a/b/c 相对路径：以当前目录作为起点，切换目录 *
cd /root/a/b/c 绝对路径：以根目录作为起点，切换目录
cd .. 返回上一级目录
cd ~ 退回当前用户的家目录

11.正确的关机方法：

[root@server ~]# reboot		//重启主机

其它一些关机命令：halt、poweroff

shutdown的一些参数使用：

shutdown [­-t 秒] [­-arkhncfF] 时间 [警告消息]

-­t sec: ­-t后面加秒数，就是过几秒后关机的意思

参数：

• -­k ：不要真关机，只是发出警告消息出去

• -­r ：在将系统的服务停掉之后重启

• -­h ：在将系统的服务停掉之后关机

• -­n ：不经过init程序，直接以shutdown的功能来关机

• -­f ：关机之后，强制略过fsck的磁盘检查

• -F: After restarting, force the fsck disk check

• -c: Cancel is already in progress The shutdown command content

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 involves gradually shutting down the currently running services 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 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: Adjust the font size of the shell window

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