1. A brief introduction to the Linux system
Linux is a free-to-use, multi-user, multi-tasking, multi-threading and multi-core CPU operating system; many medium, large and even huge projects are using Linux.
The Linux distribution is simply a package of Linux and application software. At present, the more well-known distributions on the market are: Ubuntu, RedHat, CentOS (community enterprise operating system) and so on.
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Comparison of Windows and Linux |
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Windows |
linux |
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TOLL |
TOLL |
open source free |
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software resources |
There are abundant software resources, but most of them may need to purchase copyright |
Most of the software can be freely obtained, and there are fewer choices of software with the same function |
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Technical Support |
Mainly graphical interface |
Mainly character mode, command line interface |
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safety |
Large trees attract the wind and are more prone to being attacked |
There are many released versions, and it is difficult to focus on attacks |
2. Why learn Linux?
The project server is generally a Linux system, responsible for building and maintaining the test environment, and responsible for tracking and locating bugs.
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Remote operation of Linux system through xshell and xftp
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What is xshell and xftp?
xshell is a client software, we use it on the local Windows to connect to the Linux system ( server), and operate Linux through the command line interface it provides .
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xftp is a file transfer software that can transfer files from local Windows to server Linux systems
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If the xshell connection page displays garbled characters, you need to change the default language to unicode (utf-8), click the globe icon in the menu bar to change
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System management related commands
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Login basic information
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Current login username
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# admin user prompt
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$ normal user prompt
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CPU name
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Current directory
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hostname: View the hostname
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who: query the user logged in to the system
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whoami: confirm your identity
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history: View the history of commands run by the current user
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ifconfig: command to display or set network devices, we can view the IP address of the server through this command
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ping: ping is a command under Windows, Unix and Linux systems. Ping also belongs to a communication protocol, which is part of the TCP/IP protocol. Use the "ping" command to check if the network is connected
Linux system directory structure
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The Linux file system adopts a hierarchical tree-like directory structure, in which the top level is the root main directory, and the bottom level is various subdirectories and files.
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It is very important to understand the relevant linux file directories under the root directory:
Directory manipulation commands
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pwd command displays the current path
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cd command to change directory
Usage: cd directory path
cd ./ current directory
cd .. switch to the parent directory
cd / to change to the root directory
cd ~ (or just cd ) to switch to the current user's home directory (the folder named after the username under home) /root directory
The difference between cd /opt à cd bin
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mkdir create directory
The difference between mkdir directory name –p plus p and no p
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rmdir removes empty directories
Usage: rmdir directory name
Also available: rm -rf dirname/filename
File operation command 01
In the Linux system, almost all contents including documents, commands, devices and directories are organized in the form of files and managed by files;
Common file commands are:
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touch to create a new file usage touch fanmao.txt
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vi is a commonly used and powerful text editor under linux
Press the keyboard i to enter the editing state
Exit the editing state and press the ESC key. Exit method
Quit without saving: :q! force quit
Save and exit: :wq
When entering the file:
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Enter /fanmao: search for fanmao from the beginning of the cursor to the end of the file
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Enter ?fanmao: search for fanmao from the cursor start to the beginning of the file
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Enter: set nu, display the number of lines in each line
Press the keyboard G, you can directly navigate to the end
Note: Keyboard input is all English input method for input
File operation command 02
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ls to view directories and files
Usage: ls [options] path (if there is no path, the contents of the current directory will be displayed)
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-a show all files hide files
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-l show file attributes
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cp copy command
Usage: cp [options] filename or directory target address
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-R copy directory and all directories and files under the directory directory (folder)
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cp a.txt b.txt Copy the a file and rename it as the b file (directory name)
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mv move command
Usage: mv filename or directory target directory
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mv a.txt ../ move a file to the parent directory (moving a file to another directory without renaming)
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mv a.txt ../b.txt move a file to the previous level and rename it to b file (move a file to another directory and rename it)
File Operation Command 03
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rm removes files and directories
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-f force delete
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-r delete directory
Commonly used: rm -rf file or directory
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find find files
Usage: find [path] [options]
Common options are:
① find . –name *.log Find files ending with .log in the current directory
② find / -name log Find the directory named by log in the root directory
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grep finds a character (string) in the specified file and prints the line:
filter, often with the pipe symbol |
Usage: ① grep string filename
② grep band file Find the band string in the file file
File Operation Command 04
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cat display text file content
Usage: cat filename cat filename
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head to see the first few lines
Usage: head –n 5 filename
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tail starts writing the file to standard output from the specified point, use the -f option of the tail command to easily view the log file that is changing
① tail –n 5 View the last few lines of the file name
② tail –f error.log is constantly refreshed to see the latest content
System resource query command
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ps view process (dynamic)
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-ef show all running processes and show the command to start the process
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Uid user ID, PID: process id, PPID: parent process, C: process cpu usage, Stime: time since the process started, TTY: terminal number, CMD: command name and parameters
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netstat View network status (short for net status)
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netstat –apn view all ports
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an , arrange the output in a certain order
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p , which shows which process is calling
think:
How to write if you want to filter a port or a process?
Replenish
kill: kill the process (kill -9 process number forcibly kills the process)
pipe command
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The pipe uses the "|" symbol, and establishes a pipeline between commands, taking the output of the previous command as the input of the following command
For example: ll | grep abc: The command in front of the pipeline displays the files in the current directory, and then finds the file or directory containing the abc string from the listed file names
Common situation of work: kill process (such as kill tomcat process)
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Find the process by the process name , and then kill the process
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Find the tomcat process by command | : ps –ef | grep tomcat (ps –ef is to find all running processes, and find all processes that contain the “tomcat” string through the pipe character, which is the tomcat process), for example: 5541
To kill this process, kill -9 process id (kill -9 5541)
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Find the process by port , then kill the process
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Find the process number occupying this port through the command : netstat –apn|grep 8080 Check the process according to 8080, if: 5541
Kill process: kill -9 pid (kill -9 5541)
Supplementary Knowledge Points - Beginners' Notes
Error prompt: command not found, command not found, the first reaction to see this command is to check whether the command is written incorrectly
Copy directory error in Linux cp : omitting directory—this error generally occurs, it is the directory under the directory, and cannot be copied directly -R traverses all contents
PS:
Ctrl + c to end the currently running program
Tab key use, auto-association, quick completion
Arrow keys "up", "down", search history commands, previous, next
The Linux system is a typical multi-user system. Different users are in different positions and have different permissions. In order to protect the security of the system, the Linux system has different permissions for different users to access the same file (including directory files). Provisions. In Linux, we can use the ll or ls -l command to display the attributes of a file and the user and group to which the file belongs;
like:
chmod syntax: chmod [-R] 753 (number) file or directory
Read (r): 4 Write (w): 2 Execute (x): 1
chmod –R 754 fanmao07
Test environment: chmod –R 777 fanmao07
Unzip tar.gz
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Compress the file into .tar.gz/ .tar format with the tar command, use -z to invoke gzip
For example: compress the test folder into test.tar.gz
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tar –czvf test.tar.gz test
The tar command is also used to decompress the .tar.gz/.tar format file
For example: extract test.tar.gz to get the test folder
tar –xzvf test.tar.gz
Detailed explanation of command parameters:
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-c build archive/compress
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-x unarchive/decompress
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-z Compressed files with gzip attribute
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-v show all processes
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-f use the file name, the required item, is the last parameter, followed by the file name
unzip the zip
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Compress the file into .zip format with the zip command
For example: compress the test folder into test.zip, you must include r to compress the file, otherwise an empty folder will be generated
zip –r test.zip test
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Unzip the compressed file in .zip format using the unzip command
For example: unzip the test.zip folder
unzip test.zip
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Effective immediately, invalid after restart
Start: service iptables start
shutdown: service iptables stop
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Reboot command: reboot
Others: shutdown –r now
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Shutdown command: halt
Other: shutdown -h now
poweroff
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logout: logout
Supplementary content: (common network knowledge points)
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firewall concept
The so-called "firewall" refers to a method that separates the internal network from the public access network (such as the Internet). It is actually an isolation technology to protect the internal network from the intrusion of illegal users . Network security system with external network. An information security protection system that allows or restricts the transmission of data through specific rules
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Firewall settings for online environments
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Operation and maintenance/development management and maintenance
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Firewall settings for the test environment
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If you test the intranet, you must set it and close it directly
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