Linux learning record
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1. Virtual machine network card configuration
After the server restarts, we can query the IP address of the Linux system through the linux command ip addr. The specific information is as follows:
From the figure, we can see that the IP address of the linux system has not been obtained. Why is this? This is caused by the failure to initialize the IP address because the network card is not loaded when the server is started. Then we need to modify the network initialization configuration and set the network card to initialize when the system starts.
Specific modification steps:
1). Modify the configuration items of the network card
cd / enter the root directory cd etc Enter etc Table of contents cd sysconfig Enter sysconfig Table of contents cd network-scripts Enter network-scripts vi ifcfg-ens33 edit ifcfg-ens33 document
After entering the file do the following:
①. Press i key to enter the editing state
②. Press the ↑↓ key to move the cursor, delete no, and enter yes
③. Press ESC
④. Input :wq
⑤. Press ENTER to save and exit
Remarks: The relevant instructions in Linux are used in the above operations. At present, you don't need to delve into them. We will explain them in detail later. At present, you only need to change the value of the configuration item ONBOOT in this file from no to yes.
2). Restart the virtual machine
After restarting, enter the root user name and password again, log in to the Linux system, and use the command ip addr to check the IP address.
2. Linux directory structure
After logging in to the Linux system, we need to familiarize ourselves with the directory structure of Linux. In the existing Linux system, the concept of Table of contents also exists, but there are many differences between the Table of contents structure of Linux and that of Windows. In Windows Under contents, the directory is to a certain drive letter A directory in a Linux system has the following characteristics:
A. / is the vertex of all directories
B. The directory structure is like an upside-down tree
The role and meaning of each directory under the root directory/:
3, Linux common commands
4, Linux command format
command [-options] [parameter] illustrate: command: command name [-options]: Options, which can be used to control the command or omitted [parameter]: Arguments passed to the command, which can be zero, one, or more Notice:  represents optional The command name, options, and parameters are separated by spaces
5. File directory operation commands
effect: Display the contents of the specified directory grammar: ls [-al] [dir] illustrate: -a Show all files and directories (. Hidden files at the beginning are also listed) -l In addition to the file name, also set the file type(d represents a directory,-representation file),Permissions, owner, file size and other information are listed in detail Notice: Since we use ls It is often necessary to join the command-l option, so Linux for ls -l Command provides a shorthand way of ll Common usage: ls -al View all files and directory details in the current directory ls -al /etc Check/etc All files and directory details in the directory ll View detailed information about files and directories in the current directory
effect: Used to switch the current working directory, that is, enter the specified directory grammar: cd [dirName] Special Instructions: ~ represents the user's home Table of contents . Indicates the current directory .. Indicates the parent directory of the current directory location Example: cd .. Switch to the parent directory of the current directory cd ~ switch to user's home catalogue cd /usr/local switch to/usr/local catalogue
user's home directory
root user /root
other users /home/xxx
effect: Used to display file content grammar: cat [-n] fileName illustrate: -n: Number all output lines starting from 1 Example: cat /etc/profile Check/etc under the directory profile document content
The cat command will view all the contents of the file at one time. If the file has a lot of content, it is not very convenient to view it at this time. At this time, we can pass a new command more.
effect: Display file contents in paginated form grammar: more fileName Instructions: enter scroll down one line space bar scroll down one screen b Return to previous screen q or Ctrl+C quit more Example: more /etc/profile Display in pagination/etc under the directory profile document content
When we are viewing some relatively large files, we may need to frequently query the data information at the end of the file. At this time, if the file is very large, we have to turn down the page until the last page to see the newly added data. This method is more cumbersome. At this time, we can use the tail command.
effect: See what's at the end of the file grammar: tail [-f] fileName illustrate: -f : Dynamically read the content at the end of the file and display it, usually used for the content output of the log file Example: tail /etc/profile show/etc under the directory profile The contents of the last 10 lines of the file tail -20 /etc/profile show/etc under the directory profile 20 lines at the end of the file tail -f /itcast/my.log dynamic read/itcast under the directory my.log content at the end of the file and display
effect: Create a directory grammar: mkdir [-p] dirName illustrate: -p: Make sure the directory name exists, create one if it doesn't exist. With this option, multiple directories can be created at the same time Example: mkdir itcast In the current directory, create a file named itcast subdirectory of mkdir -p itcast/test in the working directory itcast Create a directory named test subdirectories of , if itcast directory does not exist, create one
effect: delete empty directory grammar: rmdir [-p] dirName illustrate: -p: When the subdirectory is deleted and the parent directory is empty, delete it together Example: rmdir itcast delete named itcast empty directory rmdir -p itcast/test delete itcast directory named test subdirectories of , if test After directory deletion itcast directory becomes empty, it is also deleted rmdir itcast* remove the name to itcast empty directory to start with
: is a wildcard, representing any character;
rmdir itcast : remove directories starting with itcast
rmdir *itcast : remove directories ending with itcast
effect: delete file or directory grammar: rm [-rf] name illustrate: -r: Delete the directory and all files (directories) in the directory one by one, that is, recursively delete -f: Delete without confirmation Example: rm -r itcast/ delete named itcast The directory and all files in the directory must be confirmed before deletion rm -rf itcast/ No need to confirm, just delete the name itcast directory and all files in the directory rm -f hello.txt Delete without confirmation hello.txt document
Note: For commands such as rm -rf xxx, you must be careful when executing them, and delete them after confirming that they are correct to avoid accidental deletion.
6. Copy and move commands
effect: for copying files or directories grammar: cp [-r] source dest illustrate: -r: If you need to use this option when copying a directory, all subdirectories and files in the directory will be copied at this time. Example: cp hello.txt itcast/ Will hello.txt copy to itcast in the directory cp hello.txt ./hi.txt Will hello.txt Copy to the current directory and rename it hi.txt cp -r itcast/ ./itheima/ Will itcast Copy the directory and all files under the directory to itheima Under contents cp -r itcast/* ./itheima/ Will itcast Copy all files in the directory to itheima Contents
effect: Rename a file or directory, or move a file or directory to another location grammar: mv source dest Example: mv hello.txt hi.txt Will hello.txt rename to hi.txt mv hi.txt itheima/ put the file hi.txt move to itheima in the directory mv hi.txt itheima/hello.txt Will hi.txt move to itheima directory, and renamed hello.txt mv itcast/ itheima/ if itheima directory does not exist, will itcast directory renamed itheima mv itcast/ itheima/ if itheima directory exists, will itcast directory moved to itheima in the directory
7. Pack and compress commands
effect: Pack, unpack, compress, decompress files grammar: tar [-zcxvf] fileName [files] The package file suffix is.tar Indicates that the packaging is only completed, and there is no compression The package file suffix is.tar.gz Indicates that the package is also compressed illustrate: -z: z represents gzip，pass gzip command to process files, gzip Compress or decompress files -c: c represents create，i.e. create new package file -x: x represents extract，Implement restoring files from package files -v: v represents verbose，show the execution of the command -f: f represents file，Used to specify the name of the package file Example: Bale tar -cvf hello.tar ./* Package all files in the current directory, and the packaged file name is hello.tar tar -zcvf hello.tar.gz ./* Package and compress all files in the current directory, and the packaged file name is hello.tar.gz unpack tar -xvf hello.tar Will hello.tar Unpack the file and place the unpacked file in the current directory tar -zxvf hello.tar.gz Will hello.tar.gz Unzip the file and place the unzipped file in the current directory tar -zxvf hello.tar.gz -C /usr/local Will hello.tar.gz Unzip the file, and put the unzipped file in/usr/local catalogue
8. Text editing commands
8.1 Introduction to vi&vim
effect: vi The command is Linux A text editing tool provided by the system, which can edit the content of the file, similar to Windows notepad in grammar: vi fileName illustrate: 1). vim From vi A more powerful text editing tool developed, which can color the text content when editing the file, which is convenient for us to edit the file, so in actual work vim more commonly used. 2). need to use vim command, we need to complete the installation ourselves. Installation can be done with the following command: yum install vim
8.2 vim installation
Command: yum install vim
8.3 Using vim
effect: Edit the contents of the file, vim It's actually a text editor syntax: vim fileName illustrate: 1). In use vim When the command edits a file, if the specified file exists, the file is opened directly. Creates a new file if the specified file does not exist. 2). vim There are three modes in text editing, namely the command mode ( Command mode)，Insert mode ( Insert mode)and bottom row mode ( Last line mode). You can switch between these three modes. we are using vim We must pay attention to which mode we are currently in.
Three modes: - Command mode
A. In command mode, you can view the file content and move the cursor (up, down, left and right arrows, gg, G)
B. After opening the file through the vim command, it enters the command mode by default
C. The other two modes need to first enter the command mode before entering each other
| Command Mode Instructions | meaning | | ------------ | --------------------------------- | | gg | Position to the first line of text content | | G | Position to the last line of text content | | dd | Delete the data of the row where the cursor is located | | ndd | Delete the line where the current cursor is located and after n row data | | u | undo operation | | shift+zz | save and exit | | i or a or o | enter insert mode |
- insert mode
A. The content of the file can be edited in insert mode
B. Press any one of [i,a,o] in command mode to enter insert mode. After entering the insert mode, the word [insert] will appear below
C. Press the ESC key in insert mode to return to command mode
- bottom row mode
A. In the bottom line mode, you can use commands to search the file content, display the line number, exit, etc.
B. Press any one of [:,/] in command mode to enter bottom line mode
C. After entering the bottom line mode through the / method, you can search the file content
D. After entering the bottom line mode through the : method, you can enter wq (save and exit), q! (exit without saving), set nu (display line number)
9. Find command
effect: Find files in the specified directory grammar: find dirName -option fileName Example: find . –name "*.java" Find in the current directory and its subdirectories.java end file find /itcast -name "*.java" stay/itcast directory and its subdirectories.java end of file
effect: Find the specified text content from the specified file grammar: grep word fileName Example: grep Hello HelloWorld.java find HelloWorld.java appearing in the file Hello the position of the string grep hello *.java Find all in the current directory.java The file at the end contains hello the position of the string
10. Installation instructions
# install a file sudo apt install document yum -y install
11. View port command
- a (all) display all options, the default does not display LISTEN related
- t (tcp) only shows tcp related options
- u (udp) only displays udp related options
- n Refuse to display aliases, can display all the numbers into numbers.
- l Only list the service status that is in Listen (listen)
- p Displays the program name that created the associated link
- r Display routing information, routing table
- e Display extended information, such as uid, etc.
- s Statistics by protocol
- c Every fixed time, execute the netstat command.
Tip: The status of LISTEN and LISTENING can only be seen with -a or -l
11.1 List all ports
11.2 List all listening Sockets
win not found -l
# Only show listening ports netstat -l
This is the note I recorded in Youdao Cloud Notes before. Since the format is different from that of csdn, it is too troublesome to turn the table, so I use screenshots.
The learning of linux is still continuing, and the follow-up sequence will continue to be recorded in the column.
👍 Creating is not easy, please correct me if there are any mistakes, thanks for watching! Remember to like it! 👍