The cornerstone of Linux server security: understanding and using these important commands

The cornerstone of Linux server security: understanding and using these important commands

Linux servers play a vital role in the modern Internet era. They not only need to provide stability Reliable services also require strong security. In order to protect your server from malicious attacks and unauthorized access, it is crucial to understand and use some important commands correctly. This article will introduce several commonly used commands to enhance the security of Linux servers and provide corresponding code examples.

1. Network security commands

1.1 iptables: This is a very powerful network security command used to configure the firewall of a Linux server. By using iptables, we can define which network connections are allowed and which are forbidden. Below is an example showing how to disable all incoming connections and only allow connections from a specific IP address.

iptables -P INPUT DROP
iptables -A INPUT -s 允许的IP地址 -j ACCEPT

1.2 tcpdump: This is a network analysis command used to capture and analyze network traffic. It helps us detect and troubleshoot possible network security issues. Below is an example showing how to use tcpdump to capture all SSH connections coming into the server.

tcpdump -i eth0 port 22

2. User management commands

2.1 adduser: This command is used to add a new user account. In a Linux server, it is crucial to assign separate accounts to each user and limit their permissions. Below is an example showing how to create a new user using the adduser command.

adduser 新用户名

2.2 usermod: This command is used to modify the settings of an existing user account. Through usermod, we can modify the user's password, user group, home directory, etc. Below is an example showing how to use the usermod command to add a user to the sudo group.

usermod -aG sudo 用户名

3. File and permission management commands

3.1 chmod: This command is used to modify the permissions of files or directories. In a Linux server, it is very important to restrict access permissions to files and directories. Below is an example showing how to use the chmod command to set a script file so that only the owner can execute it.

chmod 700 脚本文件名

3.2 chown: This command is used to modify the ownership of a file or directory. Through chown, we can modify the owner and user group of a file or directory to the specified user and group. Below is an example that shows how to use the chown command to change the ownership of a directory to a certain user.

chown -R 用户名 目录名

4. Log management commands

4.1 tail: This command is used to view the tail content of the log file. By using tail, we can view the latest updates to the log files in real time. Below is an example showing how to use the tail command to view the last 10 lines of the /var/log/auth.log file.

tail -n 10 /var/log/auth.log

4.2 grep: This command is used to find a specific string in a text file or output. By using grep, we can quickly search and filter key information in log files. Below is an example that shows how to use the grep command to find lines containing "Failed password" in the /var/log/auth.log file.

grep "Failed password" /var/log/auth.log

Summary:

The cornerstone of Linux server security is an in-depth understanding and correct use of some important commands. This article introduces common commands in network security, user management, file and permission management, log management, etc., and provides corresponding code examples. By learning and mastering these commands, we can better protect Linux servers from malicious attacks and unauthorized access, and improve server security.

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