Table of contents
1. ls, ll commands - display data
①ls command - display data in tiles
②ll command - list display data
2. cd, pwd commands - directory switching commands
①cd command——switch working directory
②pwd command - view the current working directory
3. mkdir command - create directory
②cat command - view all file contents and display them
③more command - View file content and support page turning
①cp command - copy files and folders
②mv command - move files and folders
③rm command - delete files, folders, wildcards
①which command - View the program file storage location of the command
②find command-find files by file name
②wc command - quantity statistics
③Pipe character - the result on the left is used as the input on the right
8. echo-tail-redirector command
①echo command——output the specified content
②tail command - view the content at the end of the file
2. Linux users and permissions
1.1. Switch to root user (password required)
1.2. Switch to another user, such as jackma (no password required)
2. sudo command - add root permissions to ordinary users
2.3. View the groups to which the user belongs
2.4. Modify the group to which the user belongs
4.1. Cognitive permission information
5. chmod command - modify permission information
1. Small shortcut key operations
1.2. ctrl + d to exit or log out
7. Network requests and downloads
7.1. Use the ping command to check whether the server can be connected.
7.2. Use wget command to download files
7.3. Use the curl command to initiate a network request
8.1. Use the nmap command to check the port occupancy.
8.2. Use the netstat command to check the occupancy of the specified port.
9.2. View the specified process
10.1. Data exchange through FinalShell tool virtual machine
13. Compression and decompression
13.1.1. tar command compression
13.2. zip and unzip commands (simpler)
13.2.1. zip command to compress files
13.2.2. Unzip command to decompress files
1. Basics of Linux commands
1. ls, ll commands - display data
①ls command - display data in tiles
The ls command displays the data in a tiled manner.
②ll command - list display data
The ll command displays data in a list
-a option means: all means listing all files (including hidden files/folders)
-l option, means: display the content in the form of a list (vertically arranged) and display more information
-h means to list the file sizes in an easy-to-read form, such as K, M, G
The -h option must be used with -l
2. cd, pwd commands - directory switching commands
①cd command——switch working directory
Syntax: cd [Linux path]
②pwd command - view the current working directory
special path character
3. mkdir command - create directory
Syntax: mkdir [-p] Linux path
Create a folder in the current directory
Create a folder under the / directory
If you want to create multiple levels of directories at once, as shown below
An error will be reported because the upper-level directory test does not exist, so the test directory cannot be created. You can use the -p option to create the entire chain.
4. touch-cat-more command
①Touch command——Create file
②cat command - view all file contents and display them
This is the content of the txt.txt file
Use the cat command to view
③more command - View file content and support page turning
During the viewing process, use the space to turn pages and use q to exit viewing.
5. cp-mv-rm command
①cp command - copy files and folders
As shown above, copy the txt.txt file from the ~ directory to the move folder.
If you copy a directory, it cannot be copied
Use the -r command to copy the directory successfully.
②mv command - move files and folders
Move the txt.txt file to the move folder
If the target does not exist, it will be renamed
Move folder
③rm command - delete files, folders, wildcards
Delete txt2.txt file
Currently, there is a txt.txt file in move2, and the move2 folder cannot be deleted directly.
At this time, you need to add -r to delete it.
If used as wildcard
Delete all files or folders starting with test
6. which-find command
Use su -root to switch to administrator mode
①which command - View the program file storage location of the command
②find command-find files by file name
Search for a file named txt.txt starting from the root directory
Fuzzy matching based on wildcards
Perform fuzzy prefix matching
fuzzy suffix matching
Matches content containing txt.txt
Search based on file size
Find files larger than 1G
7. grep-wc command
① grep command - filter files
This is the content of txt.txt
Find the gcc content in the txt.txt file through grep pipe character
Find the line location of gcc and add -n
Find multiple data with the same content
②wc command - quantity statistics
The statistics are shown in the figure:
③Pipe character - the result on the left is used as the input on the right
As shown in the figure below, count the "-" data of the txt.txt file
As shown below, the number in the current directory is counted.
As shown below, find the txt.txt file in the current directory
As shown below, the input of the current directory of ls will be used as the input of the first grep, and the input of the first grep will be used as the input of the second grep.
8. echo-tail-redirector command
①echo command——output the specified content
Backtick (floating sign)
Redirector
overwrite
append write
Write the directory into the txt.txt file
②tail command - view the content at the end of the file
This is the content of the txt.txt file
By default, the last ten lines of content are viewed
View the contents of the last 5 lines
-f will continue to track and dynamically display any changes.
9. vi, vim editor
vim file name
Use i to enter compile mode
Save and exit using Esc key and :wq
2. Linux users and permissions
1. su command - switch users
1.1. Switch to root user (password required)
su - root
1.2. Switch to another user, such as jackma (no password required)
are - jackma
2. sudo command - add root permissions to ordinary users
2.1. Usage
Switch to the root user and execute the visudo command, which will automatically enter the vim compiler.
su - root
enter password
visudo
Add the following command to the last line
Add permissions for ordinary users, then:wq to save
Switch to normal user
are - jackma
Create a directory in the root directory with insufficient permissions
Use sudo command
Created successfully
2.2. Summary
You can make an ordinary command have root privileges, the syntax is:
sudo other commands
You need to execute the visudo command as the root user, and add configurations to allow ordinary users to have sudo command execution permissions.
3. Users and user groups
There are two levels of permission control in Linux, which are:
- User permission control
- Permission control for user groups
For example, for a certain file, you can control the permissions of the user or the permissions of the user group.
1. User group management
1.1. Create user group
groupadd user group name
1.2. Delete user group
groupdel user group name
2. User management
2.1. Create user
useradd [-g -d] username
- -g specifies the user's group. If -g is not specified, a group with the same name will be created and automatically joined. Specifying -g requires that the group already exists. If a group with the same name already exists, -g must be used.
- -d specifies the user HOME path. If not specified, the HOME directory defaults to:/home/username
Add to boss group
If you do not specify a directory, it will automatically be created in the home directory.
Create in the specified /home/user directory
2.2. Delete users
userdel [-r] username
- -r, delete the user's HOME directory. If -r is not used, the HOME directory will be retained when the user is deleted.
Before deletion
Delete user3
After deletion
2.3. View the groups to which the user belongs
id username
2.4. Modify the group to which the user belongs
Add the specified user to the specified group
usermod -aG user group username
Add user2 to boss2 group
2.5. Check the users in the system
getent passwd
The bottom two lines are user1 and user2
There are 7 pieces of information, namely
user name: password (x): user ID: group ID: description information (useless): HOME directory: execution terminal (default bash)
4. View permission control
4.1. Cognitive permission information
Use ls -l to view the content in list form and display permission details
- Serial number 1 represents the permission control information of files and folders.
- Serial number 2 indicates the user to whom the file and folder belongs.
- Serial number 3 indicates the user group to which the file and folder belongs.
4.2. Permission details
Permission details are divided into 10 slots in total
Example: drwxr-xr-x, means:
- This is a folder, the first letter d means
- The permissions of the user (number 2 in the upper right corner) are: r, w, x, rwx
- The permissions of the user group it belongs to (number 3 in the upper right corner) are: r, no w, x, rx (- means no such permission)
- The permissions of other users are: r, no w, x, rx
So, what does rwx stand for?
- r means read permission
- w means write permission
- x represents execution permission
The meaning of rwx is slightly different for different files and folders.
- r
- For files , you can view the file content
- For folders , you can view the contents of the folder, such as the ls command
- w
- Indicates that the file can be modified
- For folders , you can create, delete, rename, etc. operations within the folder.
- x
- Indicates that the file can be executed as a program
- For a folder , it means you can change the working directory to this folder, that is, cd to enter
5. chmod command - modify permission information
We can use the chmod command to modify the permission information of files and folders. Note that only the user who owns the file or folder or the root user can modify it.
chmod [-R] permissions file or folder
-R, applies the same operation to the entire contents of the folder
For example:
chmod u=rwx,g=rx,o=x hello.txt, change the file permissions to: rwxr-x--x
- Among them: u represents the user permissions to which user belongs, g represents group group permissions, and o represents other user permissions.
chmod -R u=rwx,g=rx,o=x test, set the permissions of the folder test and all contents in the folder to: rwxr-x--x
- In addition, there is a shortcut: chmod 751 hello.txt
Permissions before modification
Permissions after modification
6. chown command
Use the chown command to modify the users and user groups that files and folders belong to.
Ordinary users cannot change their membership to other users or groups, so this command is only applicable to root users.
chown [-R] [user] [:] [group] file or folder
- Option, -R, same as chmod, applies the same rules to all contents in the folder
- Options, users, modify the user
- Options, user groups, modify user groups to which they belong
- : used to separate users and user groups
chown root hello.txt, change the user belonging to hello.txt to root
chown:root hello.txt, change the user group to which hello.txt belongs to root
chown root:itheima hello.txt, change the user hello.txt belongs to root, and change the user group to itheima
chown -R root test, change the user belonging to the folder test to root and apply the same rules to all contents in the folder
As shown in the figure, modify the test file permissions to the root user
As shown in the figure, modify the test file permissions to the boss user group
3. Practical Linux Operations
1. Small shortcut key operations
1.1. ctrl + c force stop
If you want to forcefully stop certain programs running on Linux, you can use the shortcut key ctrl + c
If the command is entered incorrectly, you can also use the shortcut key ctrl + c to exit the current input and re-enter.
1.2. ctrl + d to exit or log out
You can use the shortcut key: ctrl + d to log out of the account.
Or exit the exclusive page of some specific programs
1.3, Clear screen
Use the shortcut key ctrl + l to clear the terminal contents
2. Software installation
yum: RPM package software manager, used to automatically install and configure Linux software, and can automatically resolve dependency issues.
yum [-y] [install] [remove] [search] software name
- Options: -y, automatic confirmation, no need to manually confirm the installation or uninstallation process
- install: install
- remove: uninstall
- search: search
The yum command requires root privileges. You can switch to root with su, or use sudo to escalate privileges.
The yum command requires an Internet connection
For example:
yum [-y] install wget, install the wget program through the yum command
yum [-y] remove wget, uninstall the wget command through the yum command
yum search wget, use the yum command to search whether there is a wget installation package
3、systemctl
The systemctl command controls the startup and shutdown of software
Many software (built-in or third-party) in Linux systems support the use of systemctl command control: start, stop, and auto-start at boot.
Software that can be managed by systemctl is also generally called: service
systemctl start | strop | status | enable | disable service name
- start start
- stop close
- status view status
- enable Enable auto-start at boot
- disable Turn off auto-start at boot
The system has many built-in services, such as:
NetworkManager, the main network service
network, deputy network service
firewalld, firewall service
sshd, ssh service (FinalShell uses this service to log in to Linux remotely)
4. Soft connection
Create soft links in the system to link files and folders to other locations. Similar to "Shortcut" in Windows system
ln -s parameter 1 parameter 2
- -s option, creates a soft connection
- Parameter 1: The linked file or folder
- Parameter 2: The destination to link to
Example:
ln -s /etc/yum.conf ~/yum.conf
ln -s /etc/yum ~/yum
5. Date, time zone
5.1. date command
You can check the system time on the command line through the date command.
date [-d] [+format string]
- -d displays the date according to the given string, generally used for date calculations
- Format string: Use specific string tags to control the displayed date format
- %Y year
- %y The last two digits of the year (00..99)
- %m month(01..12)
- %d day(01..31)
- %H hours (00..23)
- %M minutes (00..59)
- %S seconds (00..60)
- %s The number of seconds since 1970-01-01 00:00:00 UTC
5.2, ntp program
We can automatically calibrate the system time through the ntp program
Install
ntp：yum -y install ntp
Start and set up auto-start:
systemctl start ntpd
systemctl enable ntpd
When ntpd is started, it will regularly help us calibrate the system time online.
You can also calibrate manually (requires root privileges):
ntpdate -u ntp.aliyun.com
Automatically calibrate through the service URL provided by Alibaba Cloud and the ntpdate (this command will be included after installing ntp) command
6. IP address, host name
View ip address instructions
ifconfig
If you cannot use the ifconfig command, you can install
yum -y install net-tools
7. Network requests and downloads
7.1. Use the ping command to check whether the server can be connected.
You can use the ping command to check whether the specified network server is reachable.
ping [-c num] ip or host name
- Option: -c, the number of checks. If you do not use the -c option, you will continue to check an unlimited number of times.
- Parameters: ip or host name, the ip address or host name address of the server being checked
7.2. Use wget command to download files
wget is a non-interactive file downloader that can download network files from the command line
wget [-b] url
- Option: -b, optional, background download, the log will be written to the wget-log file in the current working directory
- Parameters: url, download link
Example: wget http://archive.apache.org/dist/hadoop/common/hadoop-3.3.0/hadoop-3.3.0.tar.gz
Download in the background: wget -b http://archive.apache.org/dist/hadoop/common/hadoop-3.3.0/hadoop-3.3.0.tar.gz
You can monitor the background download progress through the tail command: tail -f wget-log
7.3. Use the curl command to initiate a network request
curl can send http network requests and can be used to: download files, obtain information, etc.
curl [-0] url
- Options: -O, for downloading files, when the url is a download link, you can use this option to save the file
- Parameters: url, the network address to initiate the request
Initiate a network request to cip.cc: curl cip.cc
8. Port
View port occupancy
8.1. Use the nmap command to check the port occupancy.
Install nmap: yum -y install nmap
Syntax: nmap the IP address being viewed
As you can see, 7 ports on this machine (127.0.0.1) are now occupied by programs.
8.2. Use the netstat command to check the occupancy of the specified port.
Syntax: netstat -anp | grep port number
Install netstat: yum -y install net-tools
As shown in the figure, you can see that the current system port 6000 is occupied by the program (process number 7174), 0.0.0.0:6000, which means that the port is bound to the IP address 0.0.0.0, which means external access is allowed.
As you can see, the current system port 12345 is unused.
9. Main process management
9.1. View the process
You can view process information in the Linux system through the ps command
ps [-e -f]
- Option: -e, displays all processes
- Options: -f, display information in fully formatted form (display all information)
Generally speaking, the fixed usage is: ps -ef lists all information of all processes
ps -ef
9.2. View the specified process
We can use the pipe character with grep to filter, such as:
Accurately find redis command information
ps -ef | grep redis
Filter process information with the 6379 keyword (generally refers to filtering the 6379 process number)
ps -ef | grep 6379
9.3. Close the process
In Linux, a process can be shut down with the kill command.
kill [-9] process id
Option: -9 means forcefully shutting down the process. Not using this option will send a signal to the process asking it to shut down, but whether to shut down depends on the process's own processing mechanism.
10. File upload and download
10.1. Data exchange through FinalShell tool virtual machine
In the lower form of the FinalShell software, the Linux file system view is provided, which can be conveniently:
- Browse the file system, find the appropriate file, right-click to download, and transfer it to your local computer
- Browse the file system, find the appropriate directory, and expand the files on the local computer to easily upload data to Linux.
Upload windows files to linux using drag and drop
Download linux files to windows using download
10.2, rz, sz command
In addition to transferring files through the lower form of FinalShell, you can also transfer files through the rz and sz commands.
rz, sz commands need to be installed
yum -y install lrzsz
Usage: Use rz command directly
rz
The effect is as follows:
sz command to download
Syntax: sz file to download
As shown below:
13. Compression and decompression
13.1. tar command (complex)
You can use the tar command to perform compression and decompression operations.
Syntax: tar [-c -v -x -f -z -C] Parameter 1 Parameter 2 ... Parameter N
- -c, creates a compressed file, used in compression mode
- -v, displays the compression and decompression process, used to view the progress
- -x, decompression mode
- -f, the file to be created, or the file to be decompressed, the -f option must be the last one among all options
- -z, gzip mode, without -z it is ordinary tarball format
- -C, select the decompression destination for decompression mode
13.1.1. tar command compression
For example:
- tar -cvf test.tar 1.txt 2.txt 3.txt
Compress 1.txt 2.txt 3.txt into the test.tar file
- tar -zcvf test.tar.gz 1.txt 2.txt 3.txt
Compress 1.txt 2.txt 3.txt into the test.tar.gz file, using gzip mode
Note: If the -z option is used, it is usually the first option bit. The -f option must be the last option bit.
13.1.2. tar decompression
- tar -xvf test.tar
Unzip test.tar and extract the file to the current directory
- tar -xvf test.tar -C /home/itheima
Unzip test.tar and extract the file to the specified directory (/home/itheima)
- tar -zxvf test.tar.gz -C /home/itheima
Decompress test.tar.gz in Gzip mode and extract the file to the specified directory (/home/itheima)
Notice:
- -f option, must be the last bit in the option combination
- -z option, recommended at the beginning
- The -C option is used alone, separate from other parameters required for decompression
13.2. zip and unzip commands (simpler)
13.2.1. zip command to compress files
You can use the zip command, and the compressed file is a zip compressed package.
zip [-r] Parameter 1 Parameter 2 ... Parameter N
- -r, when compressing the included folder, you need to use the -r option, which has the same effect as the -r of rm, cp and other commands.
Example:
- zip test.zip a.txt b.txt c.txt
Compress a.txt b.txt c.txt into the test.zip file
- zip -r test.zip test itheima a.txt
Compress the test and itheima folders and the a.txt file into the test.zip file
There is no txt.zip file before compression
Compress txt.txt file to txt.zip file
13.2.2. Unzip command to decompress files
Use the unzip command to easily decompress the zip archive.
unzip [-d] parameter
- -d, specifies the location to decompress, the same as tar's -C option
- Parameters, the decompressed zip package file
unzip test.zip , extract test.zip to the current directory
unzip test.zip -d /home/itheima , unzip test.zip to the specified folder (/home/itheima)
There is no txt.txt file before decompression
After decompressing txt.zip, there is a txt.txt file
