Package Management¶

1. Package Management Concepts¶

Package managers automate software installation, updates, and removal.

┌─────────────────────────────────────────────────────────┐
│                    Package Repository                    │
│              (Repository / Mirror)                       │
└────────────────────────┬────────────────────────────────┘
                         │
                         ▼
┌─────────────────────────────────────────────────────────┐
│                    Package Manager                       │
│         APT (Debian/Ubuntu) / DNF (RHEL/CentOS)         │
│                                                          │
│  • Automatic dependency resolution                       │
│  • Version management                                    │
│  • Integrity verification                                │
└─────────────────────────────────────────────────────────┘

Package Managers by Distribution¶

Distribution	Package Format	Low-level Tool	High-level Tool
Ubuntu/Debian	.deb	dpkg	apt
CentOS/RHEL 8+	.rpm	rpm	dnf
CentOS/RHEL 7	.rpm	rpm	yum
Fedora	.rpm	rpm	dnf

2. APT (Ubuntu/Debian)¶

Update Repository¶

# Update package list (required before installation)
sudo apt update

Install Packages¶

# Install package
sudo apt install nginx

# Multiple packages
sudo apt install nginx php mysql-server

# Install without confirmation
sudo apt install -y vim

# Install specific version
sudo apt install nginx=1.18.0-0ubuntu1

Remove Packages¶

# Remove package only
sudo apt remove nginx

# Remove package with configuration files
sudo apt purge nginx

# Remove unused dependencies
sudo apt autoremove

# Remove with automatic cleanup
sudo apt remove --autoremove nginx

Update Packages¶

# Upgrade all installed packages
sudo apt upgrade

# Distribution upgrade (including dependency changes)
sudo apt full-upgrade

# Upgrade distribution version
sudo do-release-upgrade

Search Packages¶

# Search for package
apt search nginx

# Package information
apt show nginx

# List installed packages
apt list --installed

# List upgradable packages
apt list --upgradable

Clean Cache¶

# Clean downloaded package files
sudo apt clean

# Clean only old package files
sudo apt autoclean

3. DNF/YUM (CentOS/RHEL)¶

DNF (RHEL 8+, CentOS 8+, Fedora)¶

# Check for updates
sudo dnf check-update

# Install package
sudo dnf install nginx

# Multiple packages
sudo dnf install nginx php mysql-server

# Install without confirmation
sudo dnf install -y vim

# Remove package
sudo dnf remove nginx

# Remove package with dependencies
sudo dnf autoremove nginx

# Update all packages
sudo dnf upgrade

# Search for package
dnf search nginx

# Package information
dnf info nginx

# List installed packages
dnf list installed

# Clean cache
sudo dnf clean all

YUM (RHEL 7, CentOS 7)¶

# Install package
sudo yum install nginx

# Remove package
sudo yum remove nginx

# Update packages
sudo yum update

# Search for package
yum search nginx

# Package information
yum info nginx

4. Repository Management¶

Ubuntu/Debian Repositories¶

/etc/apt/sources.list¶

# View repository list
cat /etc/apt/sources.list

# Additional repository directory
ls /etc/apt/sources.list.d/

Add PPA (Personal Package Archive)¶

# Add PPA
sudo add-apt-repository ppa:ondrej/php

# Remove PPA
sudo add-apt-repository --remove ppa:ondrej/php

# Update after adding repository
sudo apt update

Add External Repository¶

# Docker repository example
# 1. Add GPG key
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

# 2. Add repository
echo "deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

# 3. Update and install
sudo apt update
sudo apt install docker-ce

CentOS/RHEL Repositories¶

Repository List¶

# List repositories
dnf repolist

# Detailed information
dnf repolist -v

# Repository configuration location
ls /etc/yum.repos.d/

Add Repository¶

# EPEL repository (Extra Packages for Enterprise Linux)
sudo dnf install epel-release

# Add repository file directly
sudo vi /etc/yum.repos.d/custom.repo

Repository file format:

[custom-repo]
name=Custom Repository
baseurl=https://example.com/repo/
enabled=1
gpgcheck=1
gpgkey=https://example.com/RPM-GPG-KEY

5. Package Information¶

Ubuntu/Debian (dpkg)¶

# List installed packages
dpkg -l

# Search for specific package
dpkg -l | grep nginx

# Package status
dpkg -s nginx

# List files installed by package
dpkg -L nginx

# Find package that owns file
dpkg -S /usr/sbin/nginx

CentOS/RHEL (rpm)¶

# List installed packages
rpm -qa

# Search for specific package
rpm -qa | grep nginx

# Package information
rpm -qi nginx

# List files installed by package
rpm -ql nginx

# Find package that owns file
rpm -qf /usr/sbin/nginx

6. Source Compilation¶

Compile software not available in repositories.

Install Build Tools¶

Ubuntu/Debian¶

sudo apt install build-essential

CentOS/RHEL¶

sudo dnf groupinstall "Development Tools"
sudo dnf install gcc gcc-c++ make

Compilation Process¶

# 1. Download and extract source
wget https://example.com/software-1.0.tar.gz
tar -xzvf software-1.0.tar.gz
cd software-1.0

# 2. Check dependencies and configure
./configure --prefix=/usr/local

# 3. Compile
make

# 4. Install
sudo make install

# 5. Clean (optional)
make clean

checkinstall (Manage as Package)¶

# Install
sudo apt install checkinstall

# Use instead of make install
sudo checkinstall

# Can be removed later with package manager

7. Practical Patterns¶

System Update¶

Ubuntu/Debian¶

# Update script
#!/bin/bash
sudo apt update
sudo apt upgrade -y
sudo apt autoremove -y
sudo apt clean

CentOS/RHEL¶

# Update script
#!/bin/bash
sudo dnf check-update
sudo dnf upgrade -y
sudo dnf autoremove -y
sudo dnf clean all

Install Essential Packages¶

Ubuntu/Debian¶

# Server basic packages
sudo apt install -y \
    vim \
    curl \
    wget \
    git \
    htop \
    net-tools \
    unzip \
    tree

CentOS/RHEL¶

# Server basic packages
sudo dnf install -y \
    vim \
    curl \
    wget \
    git \
    htop \
    net-tools \
    unzip \
    tree

Package Pinning (Prevent Version Upgrade)¶

Ubuntu/Debian¶

# Pin package
sudo apt-mark hold nginx

# Unpin package
sudo apt-mark unhold nginx

# List pinned packages
apt-mark showhold

CentOS/RHEL¶

# Install versionlock plugin
sudo dnf install dnf-plugin-versionlock

# Pin package
sudo dnf versionlock add nginx

# Unpin package
sudo dnf versionlock delete nginx

# List pinned packages
dnf versionlock list

8. Troubleshooting¶

Dependency Issues¶

Ubuntu/Debian¶

# Fix broken packages
sudo apt --fix-broken install

# Force install (caution)
sudo apt install -f

# Recover dpkg configuration
sudo dpkg --configure -a

CentOS/RHEL¶

# Clean dependencies
sudo dnf clean all
sudo dnf makecache

# Remove and reinstall problematic package
sudo dnf remove package_name
sudo dnf install package_name

Lock Issues¶

Ubuntu/Debian¶

# Release apt lock (when another apt is running)
sudo rm /var/lib/dpkg/lock-frontend
sudo rm /var/lib/apt/lists/lock
sudo rm /var/cache/apt/archives/lock
sudo dpkg --configure -a

9. CentOS End-of-Life and Migration¶

CentOS EOL Status¶

CentOS Linux has reached end-of-life (EOL) for all versions:

CentOS 8: EOL on December 31, 2021
CentOS 7: EOL on June 30, 2024

CentOS Stream is now the only CentOS variant available, but it serves a different purpose: - CentOS Stream is a rolling-release development platform - Positioned upstream of RHEL (not downstream like CentOS Linux) - Not a 1:1 binary-compatible RHEL replacement - Receives updates before RHEL (cutting-edge, less stable)

Migration Options¶

Organizations using CentOS need to migrate to alternative distributions:

Distribution	Maintainer	RHEL Compatibility	Cost
Rocky Linux	Rocky Enterprise Software Foundation	1:1 binary compatible	Free
AlmaLinux	AlmaLinux OS Foundation (CloudLinux)	1:1 binary compatible	Free
Oracle Linux	Oracle	Binary compatible	Free
RHEL	Red Hat	Original	Paid (free dev subscriptions available)

Rocky Linux¶

Founded by Gregory Kurtzer (original CentOS co-founder)
Community-driven, non-profit
1:1 binary compatible with RHEL
Active community and corporate support

# Check current CentOS version
cat /etc/redhat-release

# Migrate to Rocky Linux (CentOS 8)
sudo curl -O https://raw.githubusercontent.com/rocky-linux/rocky-tools/main/migrate2rocky/migrate2rocky.sh
sudo bash migrate2rocky.sh -r

AlmaLinux¶

Backed by CloudLinux Inc.
1:1 binary compatible with RHEL
Strong commercial support
Well-established infrastructure

# Migrate to AlmaLinux (CentOS 8)
sudo curl -O https://raw.githubusercontent.com/AlmaLinux/almalinux-deploy/master/almalinux-deploy.sh
sudo bash almalinux-deploy.sh

Oracle Linux¶

Maintained by Oracle
Binary compatible with RHEL
Option to use Unbreakable Enterprise Kernel (UEK)
Free to use and distribute

# Migrate to Oracle Linux (CentOS 7/8)
sudo curl -O https://raw.githubusercontent.com/oracle/centos2ol/main/centos2ol.sh
sudo bash centos2ol.sh

Key Differences: Rocky vs AlmaLinux¶

Aspect	Rocky Linux	AlmaLinux
Governance	Community-driven foundation	CloudLinux-backed foundation
Funding	Donations, sponsors	CloudLinux Inc. + sponsors
Release Cycle	Typically tracks RHEL closely	Typically tracks RHEL closely
Live Patching	Limited	Available (paid KernelCare)
Commercial Support	Third-party vendors	CloudLinux + partners

Both distributions are excellent choices and have very similar features. The choice often comes down to: - Rocky Linux: If you prefer community-driven governance and CentOS legacy - AlmaLinux: If you want corporate backing and optional commercial support

Migration Best Practices¶

Test first: Migrate a non-production system first
Backup: Full system backup before migration
Check compatibility: Review third-party software compatibility
Update before migration: Ensure CentOS is fully updated
Verify after migration: Check services and applications post-migration

# Pre-migration checklist
# 1. List installed packages
rpm -qa > /root/packages-before.txt

# 2. Backup important configs
sudo tar -czf /root/etc-backup.tar.gz /etc

# 3. Update system fully
sudo yum update -y

# 4. Reboot to latest kernel
sudo reboot

# Post-migration verification
# 1. Check OS version
cat /etc/redhat-release

# 2. Verify package count
rpm -qa | wc -l

# 3. Check for broken dependencies
sudo dnf check

# 4. Verify services
sudo systemctl list-units --state=failed

Recommendation¶

For most users migrating from CentOS: - Choose Rocky Linux or AlmaLinux for production workloads - Both provide stable, enterprise-grade RHEL replacements - Avoid CentOS Stream for production unless you need cutting-edge features - Consider RHEL if you need official Red Hat support

10. Practice Exercises¶

Exercise 1: Search and Install Package¶

Ubuntu/Debian¶

# Search for htop
apt search htop

# Check information
apt show htop

# Install
sudo apt update
sudo apt install -y htop

# Verify
htop --version

CentOS/RHEL¶

# Search for htop
dnf search htop

# Check information
dnf info htop

# Install
sudo dnf install -y htop

# Verify
htop --version

Exercise 2: Check Package Information¶

Ubuntu/Debian¶

# Count installed packages
dpkg -l | grep "^ii" | wc -l

# Files installed by specific package
dpkg -L bash | head -20

# Find package that owns file
dpkg -S /bin/bash

CentOS/RHEL¶

# Count installed packages
rpm -qa | wc -l

# Files installed by specific package
rpm -ql bash | head -20

# Find package that owns file
rpm -qf /bin/bash

Exercise 3: System Update¶

Ubuntu/Debian¶

# Update repository list
sudo apt update

# Check upgradable packages
apt list --upgradable

# Upgrade
sudo apt upgrade -y

# Clean up
sudo apt autoremove -y
sudo apt clean

CentOS/RHEL¶

# Check for updates
sudo dnf check-update

# Upgrade
sudo dnf upgrade -y

# Clean up
sudo dnf autoremove -y
sudo dnf clean all

Exercise 4: Remove Package¶

# Ubuntu/Debian
sudo apt remove htop
sudo apt purge htop    # Also remove configuration files
sudo apt autoremove

# CentOS/RHEL
sudo dnf remove htop
sudo dnf autoremove

Next Steps¶

Let's learn about shell scripting in 09_Shell_Scripting.md!