What is the Linux port command?
Linux view port command
The first one:
lsof -i:port number
Recommendation: "Linux Tutorial"
Second type:
netstat -nltp | grep port number
-a: Display all connections and listening ports of this machine
-n: In the form of network IP address, display the currently established effective connections and ports
-r: Display routing table information
-s: Display statistics by protocol
-v: Display currently valid connections
-t: Display all TCP protocol connections
-u : Display all UDP protocol connection status
-i: Display the status of the automatically configured port
-l: Only display the service network status with the connection status listening
-p: Display pid/program name
Several statuses of TCP connection
ESTABLISHED 已建立 CLOSED 已关闭 LISTENING 正在监听 FIN-WAIT-2 等待连接关闭 TIME-WAIT 等待足够时间,确保服务器正常关闭该连接
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Linux user management and security can be achieved through the following steps: 1. Create users and groups, using commands such as sudouseradd-m-gdevelopers-s/bin/bashjohn. 2. Bulkly create users and set password policies, using the for loop and chpasswd commands. 3. Check and fix common errors, home directory and shell settings. 4. Implement best practices such as strong cryptographic policies, regular audits and the principle of minimum authority. 5. Optimize performance, use sudo and adjust PAM module configuration. Through these methods, users can be effectively managed and system security can be improved.

The core operations of Linux file system and process management include file system management and process control. 1) File system operations include creating, deleting, copying and moving files or directories, using commands such as mkdir, rmdir, cp and mv. 2) Process management involves starting, monitoring and killing processes, using commands such as ./my_script.sh&, top and kill.

Shell scripts are powerful tools for automated execution of commands in Linux systems. 1) The shell script executes commands line by line through the interpreter to process variable substitution and conditional judgment. 2) The basic usage includes backup operations, such as using the tar command to back up the directory. 3) Advanced usage involves the use of functions and case statements to manage services. 4) Debugging skills include using set-x to enable debugging mode and set-e to exit when the command fails. 5) Performance optimization is recommended to avoid subshells, use arrays and optimization loops.

Linux is a Unix-based multi-user, multi-tasking operating system that emphasizes simplicity, modularity and openness. Its core functions include: file system: organized in a tree structure, supports multiple file systems such as ext4, XFS, Btrfs, and use df-T to view file system types. Process management: View the process through the ps command, manage the process using PID, involving priority settings and signal processing. Network configuration: Flexible setting of IP addresses and managing network services, and use sudoipaddradd to configure IP. These features are applied in real-life operations through basic commands and advanced script automation, improving efficiency and reducing errors.

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The core components of Linux include kernel, shell, file system, process management and memory management. 1) Kernel management system resources, 2) shell provides user interaction interface, 3) file system supports multiple formats, 4) Process management is implemented through system calls such as fork, and 5) memory management uses virtual memory technology.

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