https://drive.google.com/file/d/1IrPUrg9OlJhm6Wd0XfKfFJq54cZGPZ6S/view?usp=sharing

1. Understanding Kernel Management

Key Concepts

• Default Kernel: RHEL/CentOS ships with a stable, tested kernel (e.g., 4.18.0-448.el8.x86_64)
• Mainline Kernel (ML): Latest upstream kernel from kernel.org (via ELRepo)
• GRUB Management: Never edit /boot/grub2/grub.cfg directly—use configuration tools

⚠️ Critical Warning:

Mainline kernels lack RHEL-specific patches and may cause stability issues.

Only use for testing or specific hardware support.

2. Installing ELRepo Repository

Add ELRepo (RHEL 8 Compatible)

# Install ELRepo GPG key
sudo rpm --import <https://www.elrepo.org/RPM-GPG-KEY-elrepo.org>

# Install ELRepo for RHEL 8 (NOT RHEL 7!)
sudo dnf install <https://www.elrepo.org/elrepo-release-8.el8.elrepo.noarch.rpm> -y

# Verify repositories
sudo dnf repolist all | grep elrepo

💡 Note:

Your original command used RHEL 7 repo (elrepo-release-7.el7...)—this causes errors on RHEL 8!

3. Installing Mainline Kernel

Install Latest Mainline Kernel

# List available kernels
sudo dnf --enablerepo=elrepo-kernel list available | grep kernel-ml

# Install mainline kernel
sudo dnf --enablerepo=elrepo-kernel install kernel-ml -y

# Verify installation
ls /boot/vmlinuz-*    # Should show new kernel (e.g., vmlinuz-6.1.0-1.el8.elrepo.x86_64)

🔍 Kernel Naming:

• kernel-ml = Mainline kernel
• kernel-lt = Long-term support kernel

4. Managing GRUB Boot Entries