與CentOS和RHEL的YUM和DNF掌握軟件包管理

Introduction: Mastering CentOS/RHEL Software Management

Effective software package management is paramount for Linux system administrators using CentOS and Red Hat Enterprise Linux (RHEL). This guide provides a comprehensive overview of using Yum and DNF, the primary package managers for these distributions, to ensure system security, updates, and optimal performance. While Yum was the standard in earlier versions (CentOS/RHEL 7 and below), DNF (Dandified Yum) has become the default in CentOS 8 and RHEL 8 and beyond, offering superior speed, dependency resolution, and memory management.

Yum and DNF: A Detailed Comparison

Yum (Yellowdog Updater, Modified): A long-standing package manager, Yum automates the installation, updating, and removal of software packages, handling dependencies effectively.

DNF (Dandified Yum): The successor to Yum, DNF boasts improved performance, reduced memory footprint, enhanced dependency handling, and increased security features. In newer CentOS/RHEL versions, Yum often acts as a symbolic link to DNF.

Key DNF Advantages over Yum:

• Significantly faster package management
• Optimized memory usage
• Robust dependency resolution
• Enhanced security and modular design

Repository Management: Keeping Your System Current

Before any software installation or update, ensure your system repositories are up-to-date.

Using Yum (CentOS/RHEL 7 and earlier):

yum check-update
yum update

Using DNF (CentOS/RHEL 8 and later):

dnf check-update
dnf update

The update command synchronizes package lists and applies available updates.

Software Installation, Removal, and Search

Installation:

Yum: yum install package-name

DNF: dnf install package-name (e.g., dnf install httpd -y installs Apache; -y auto-confirms)

Removal:

Yum: yum remove package-name

DNF: dnf remove package-name (e.g., dnf remove httpd -y removes Apache)

Searching:

Yum: yum search package-name

DNF: dnf search package-name (e.g., dnf search nginx searches for Nginx packages)

Package Information and Management

Listing Installed Packages:

Yum: yum list installed

DNF: dnf list installed (e.g., dnf list installed | grep httpd checks for Apache)

Detailed Package Information:

Yum: yum info package-name

DNF: dnf info package-name (e.g., dnf info vim shows Vim details)

Managing Software Groups:

List Groups: dnf group list

Install Group: dnf group install "Development Tools" -y

Remove Group: dnf group remove "Development Tools" -y

Advanced Package Management Techniques

Dependency Handling:

• Check Dependencies: dnf deplist package-name
• Remove Unused Dependencies: dnf autoremove

Cache Management:

Yum: yum clean all

DNF: dnf clean all

Repository Control:

Enable/disable repositories (temporarily): dnf --enablerepo=repository-name install package-name or dnf --disablerepo=repository-name install package-name. For permanent changes, modify /etc/yum.repos.d/ files.

DNF Transaction History:

• View History: dnf history
• Undo Transaction: dnf history undo transaction-id
• Rollback: dnf history rollback transaction-id

Local RPM Installation:

Yum: yum localinstall package.rpm

DNF: dnf install package.rpm

Security Updates:

• Check Security Updates: dnf updateinfo list security
• Apply Security Updates: dnf update --security

Conclusion: Optimizing Your CentOS/RHEL System

Proficient package management is vital for maintaining secure and efficient CentOS/RHEL systems. While Yum served its purpose well, DNF's enhancements make it the preferred choice for modern deployments. By mastering the commands outlined in this guide, you can effectively manage your software, ensuring system stability and security.

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