Linux Operating System Basics

1.Linux Introduction

Linux is a free and open-source operating system with many different versions of Linux, but they all use the Linux kernel. Linux can be installed in a variety of computer hardware devices, such as mobile phones, tablets, routers, desktop computers

2.Linux Introduction

Features of 3.Linux

1. Multi-user, multi-tasking, rich network functions, reliable system security, good portability, standard compatibility, good user interface, excellent speed performance
2. Open source

4.CentOS

1. Mainstream: The current Linux operating system is mainly used in production environments, mainstream enterprise Linux systems are still redhat or CentOS
2. Free: RedHat and CentOS are not very different, based on Red Hat Linux is free to use the source code of the Enterprise CentOS is a level Linux distribution
3. Easy to update: the CentOS exclusive yum command supports online upgrades, updates the system instantly, and does not require money to purchase support services like Redhat!

5.CentOS Mirror

CentOS Website: http://www.centos.org/
CentOS Sohu Image: http://mirrors.sohu.com/centos/
CentOS NetEase Image: http://mirrors.163.com/centos/
CentOS Beijing Polytechnic University Image: http://mirror.bit.edu.cn/centos/

6.Linux directory Structure

7.Linux command

• First you have to be man.

1. Internal command: Echo
To view internal command help: assist Echo or man Echo

2. External command: LS
View external command help: LS--help or man ls or info ls

Type of 3.man document (1~9)
Man man-pages view the meaning of each type of representation
Man 5 passwd (5 for profile level)


4. Shortcut keys:
CTRL + C: Stop process

CTRL + L: Clear screen

CTRL + R: Search History commands

5. Good at using the TAB key to complete the command

• used in
  
  1. Go to the user root directory
  CD ~ or CD
  
  2. View your current directory
  pwd
  
  3. Go to the Itcast user root directory
  CD ~itcast
  
  4. Return to the original directory
  CD-
  
  5. Go back to the top level directory
  CD..
  
  6. View all files under the Itcast user's root directory
  Ls-la
  
  7. Create a Itcast folder in the root directory
  Mkdir/itcast
  
  8. Create SRC and webroot two folders under the/itcast directory
  created separately: MKDIR/ITCAST/SRC
  Mkdir/itcast/webroot
  create simultaneously: Mkdir/itcast/{src,webroot}
  
  go to the/itcast directory and create the. Classpath and Readme files in this directory
  create separately: touch. Classpath
  Touch README
  Create simultaneously: Touch {. Classpath,readme}
  
  View all files under the/itcast directory
  Ls-la
  
  Create a Test.txt file under the/itcast directory and write the content "This is test"
  echo "This is Test" > Test.txt
  
  Take a look at the contents of Test.txt
  Cat Test.txt
  More test.txt
  Less test.txt
  
  Append write to Readme file "Please read Me first"
  echo "Please read Me first" >> README
  
  Append the contents of the Test.txt to the Readme file
  cat Test.txt >> README
  
  Copy all files under the/itcast directory to/itcast-bak
  cp-r/itcast/itcast-bak
  
  go to the/itcast-bak directory, move the test.txt to the SRC directory, and modify the file name to Student.java
  MV Test.txt Src/student.java
  
  Create a struts.xml in the SRC directory
  > Struts.xml
  
  Delete all XML types of files
  RM-RF *.xml
  
  Delete the/itcast-bak directory and all files below
  Rm-rf/itcast-bak
  
  go back to the/itcast directory to see how many words the Readme file has and how many fewer lines
  wc-w README
  wc-l README
  
  Go back to the root directory, package the/itcast directory first, and then use gzip to compress
  step through: TAR-CVF Itcast.tar itcast
  gzip Itcast.tar
  One-Step completion: TAR-ZCVF itcast.tar.gz itcast
            
  unzip it, and then cancel the package
  step through: gzip-d itcast.tar.gz or Gunzip itcast.tar.gz
  One-Step completion: TAR-ZXVF itcast.tar.gz
  
  pack The/itcast directory first, compress it with bzip2, and save it to the/tmp directory
  tar-jcvf/tmp/itcast.tar.bz2 Itcast
  
  unzip the/tmp/itcast.tar.bz2 to the/usr directory
  TAR-JXVF itcast.tar.bz2-c/usr/
• Users and Groups

Add a Tom user, set it to belong to the Users group, and add comment information
step through: Useradd Tom
usermod-g users Tom
usermod-c "hr Tom" Tom
One-Step completion: Useradd-g users-c "hr Tom" Tom

set the password for the Tom user
passwd Tom

change Tom User's login name to Tomcat
usermod-l Tomcat Tom

add tomcat to the SYS and root groups
usermod-g sys,root Tomcat

View the group information for Tomcat
groups Tomcat

Add a Jerry user and set a password
Useradd Jerry
passwd Jerry

Add a cross-America group
Groupadd America

add Jerry to the America group
Usermod-g America Jerry

Remove the Tomcat user from the root group and the SYS group
gpasswd-d Tomcat Root
gpasswd-d Tomcat SYS

Modify the America group name to AM
Groupmod-n AM America

• Permissions

Create A.txt and B.txt files, set them to their owner and group writable, but not others:
chmod ug+w,o-w a.txt B.txt

Create C.txt file Everyone can write and execute
chmod a=wx c.txt or chmod 666 c.txt

Set all files and subdirectories in the/itcast directory to be readable by anyone
Chmod-r A+r/itcast

The owner of all files and subdirectories under the/itcast directory is set to root, and the user has a group of users
Chown-r Root:users/itcast

Sets all files in the current directory and subdirectories to Itcast, set to users
Chown-r Itcast:users *

Use of 8.VIM

Here do not write, there are a lot of information on the Internet, it is recommended to remember the use of commands, to the level of memory,

Linux operating System Fundamentals