Is the Linux 4.18 kernel heading your way?

Introduction

The Linux kernel is the core component of every Linux distribution, serving as the bridge between hardware and software. When a new kernel version is released, it brings improvements in hardware support, performance optimizations, security patches, and new features. Understanding kernel versions and how they propagate through different distributions is crucial for system administrators and Linux enthusiasts.

The recently released 4.18 Linux kernel has already moved up to 4.18.5 with stability improvements. How soon it lands on your system or network depends a lot on which Linux distributions you use.

How soon the 4.18 kernel lands on your system or network depends a lot on which Linux distributions you use. It may be heading your way or you may already be using it.

Understanding Linux Kernel Versioning

Linux kernel versions follow a specific numbering scheme:

• Major version: First number (e.g., 4 in 4.18)
• Minor version: Second number (e.g., 18 in 4.18)
• Patch level: Third number (e.g., 5 in 4.18.5)

Each release represents different levels of changes:

• Major releases: Significant architectural changes (rare, last was 2.6 to 3.0)
• Minor releases: New features, driver updates, performance improvements
• Patch releases: Bug fixes and security updates

How Different Distributions Handle Kernel Updates

If you have ever wondered whether the same kernel is used in all Linux distributions, the answer is that all Linux distributions use the same kernel more or less, but there are several big considerations that make that “more or less” quite significant:

1. Distribution-Specific Kernel Modifications

Most distributions add or remove code to make the kernel work best for them. Some of these changes might eventually work their way back to the top of the code heap where they will be merged into the mainstream, but they’ll make the distribution’s kernel unique — at least for a while.

Examples of distribution-specific modifications:

• Ubuntu: Adds AUFS support, custom patches for better desktop performance
• Red Hat: Extensive backporting of security fixes to stable kernels
• Arch Linux: Minimal patches, stays close to vanilla kernel
• Debian: Conservative patching, focuses on stability

2. Kernel Update Policies by Distribution

Some releases intentionally hold back and don’t use the very latest version of the kernel in order to ensure a more predictable and stable environment. This is particularly true of versions that are targeted for commercial distribution. For example, RHEL (Red Hat Enterprise Edition) will not be nearly as aggressively updated as Fedora.

Distribution kernel update strategies:

Bleeding Edge (Latest Kernels)

• Arch Linux: Updates to new kernel within days of release
• Fedora: Adopts new kernels within weeks
• openSUSE Tumbleweed: Rolling release with frequent kernel updates

Balanced Approach

• Ubuntu (non-LTS): Updates kernel with each 6-month release
• openSUSE Leap: Stable kernel with selective backports
• Manjaro: Holds packages for testing before release

Conservative (Stability First)

• RHEL/CentOS: Stays on one kernel version for years, backports fixes
• Ubuntu LTS: Minimal kernel updates during 5-year support cycle
• Debian Stable: Kernel updated only for critical security issues
• SUSE Enterprise: Long-term kernel maintenance

3. Linux-libre: Freedom-Focused Kernel

Some distributions use a fork called Linux-libre, which is Linux without any proprietary drivers built in. It omits software that does not include its source code, has its source code obfuscated, or is released under proprietary licenses.

Distributions using Linux-libre:

• Parabola GNU/Linux-libre: Fully free Arch derivative
• Trisquel: Ubuntu-based free software distribution
• GuixSD: Functional package management with libre kernel
• Hyperbola: Long-term support with freedom focus

Key Features in Linux Kernel 4.18

Hardware Support Improvements

• AMD GPU Support: Better support for Radeon Vega graphics
• Intel Improvements: Cannonlake graphics support
• ARM Enhancements: New SoC support for embedded devices
• Network Drivers: Updated Wi-Fi and Ethernet drivers

Performance Optimizations

• NUMA balancing: Improved memory access on multi-socket systems
• Scheduler improvements: Better CPU utilization
• File system enhancements: Faster I/O operations
• Network stack: Reduced latency for high-speed networking

Security Enhancements

• Spectre/Meltdown mitigations: Continued hardening against CPU vulnerabilities
• Kernel hardening: Stack protection improvements
• Cryptography updates: New encryption algorithms

Checking Your Current Kernel Version

Command Line Methods

# Display kernel version
uname -r

# Detailed kernel information
uname -a

# Kernel version and distribution details
cat /proc/version

# Show installed kernels (Debian/Ubuntu)
dpkg --list | grep linux-image

# Show installed kernels (RHEL/Fedora/CentOS)
rpm -qa | grep kernel

# Check kernel release and architecture
hostnamectl

Graphical Methods

• GNOME: Settings → About → System Details
• KDE: System Settings → System Information
• XFCE: Applications → Settings → About

Updating Your Kernel

Ubuntu/Debian

# Update package list
sudo apt update

# Upgrade kernel and all packages
sudo apt upgrade

# Install specific kernel version
sudo apt install linux-image-4.18.0-25-generic

# Reboot to use new kernel
sudo reboot

Fedora/RHEL/CentOS

# Update all packages including kernel
sudo dnf upgrade

# Install specific kernel (Fedora)
sudo dnf install kernel-4.18.16

# CentOS/RHEL - enable new kernel repo first
sudo yum update kernel

# Reboot
sudo reboot

Arch Linux

# Update entire system (including kernel)
sudo pacman -Syu

# Install LTS kernel alongside
sudo pacman -S linux-lts

# Reboot to new kernel
sudo reboot

Managing Multiple Kernels

GRUB Bootloader Configuration

# List installed kernels
sudo ls /boot/vmlinuz*

# Edit GRUB defaults
sudo nano /etc/default/grub

# Update GRUB configuration
sudo update-grub  # Debian/Ubuntu
sudo grub2-mkconfig -o /boot/grub2/grub.cfg  # RHEL/Fedora

# Set default kernel
sudo grub-set-default 0  # 0 = first kernel in list

Removing Old Kernels

# Ubuntu - autoremove old kernels
sudo apt autoremove

# Manually remove specific kernel (Ubuntu)
sudo apt remove linux-image-4.15.0-20-generic

# Fedora/CentOS - remove old kernels
sudo dnf remove kernel-4.15.0

# Keep only 2 latest kernels (Fedora)
sudo dnf install yum-utils
sudo package-cleanup --oldkernels --count=2

Kernel Compilation and Custom Kernels

For advanced users who need specific features or optimizations:

# Install build dependencies (Ubuntu)
sudo apt install build-essential libncurses-dev bison flex libssl-dev libelf-dev

# Download kernel source
wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.18.tar.xz
tar -xf linux-4.18.tar.xz
cd linux-4.18

# Configure kernel
make menuconfig

# Compile kernel (use all CPU cores)
make -j$(nproc)

# Install modules and kernel
sudo make modules_install
sudo make install

# Update bootloader
sudo update-grub

Troubleshooting Kernel Issues

Boot Problems After Kernel Update

If your system doesn’t boot after a kernel update:

1. Reboot and select previous kernel from GRUB menu
2. Once booted, remove problematic kernel
3. Check system logs: sudo journalctl -b -1
4. Report bugs to distribution maintainers

Hardware Not Working After Update

# Check for missing firmware
dmesg | grep -i firmware

# Install firmware packages
sudo apt install linux-firmware  # Ubuntu
sudo dnf install linux-firmware  # Fedora

# Check loaded kernel modules
lsmod

# Load missing module manually
sudo modprobe module_name

Frequently Asked Questions

What is the difference between a kernel upgrade and a kernel update?

A kernel update typically refers to patch-level changes (e.g., 4.18.5 to 4.18.6) that fix bugs and security issues. A kernel upgrade involves moving to a new minor or major version (e.g., 4.18 to 4.19 or 4.x to 5.x) which includes new features and significant changes.

How often should I update my Linux kernel?

For desktop systems, update whenever your distribution provides updates. For production servers, follow your distribution’s recommended update schedule – typically monthly for patches, and only during maintenance windows for major kernel upgrades after thorough testing.

Can I run multiple kernel versions simultaneously?

You can have multiple kernel versions installed, but only one runs at a time. During boot, GRUB allows you to select which kernel to load. This is useful for testing new kernels while keeping a known-good fallback.

What happens if I don’t update my kernel?

Running outdated kernels exposes you to security vulnerabilities, missing hardware support, and performance issues. Critical security patches are often only available in newer kernels, making updates essential for secure systems.

How do I know if my hardware requires a specific kernel version?

Check hardware manufacturer specifications and Linux hardware databases like linux-hardware.org. Newer hardware generally requires newer kernels – cutting-edge devices may need kernel 5.0+ while legacy hardware works fine with 4.x kernels.

Why does RHEL use such old kernel versions?

RHEL prioritizes stability and long-term support over bleeding-edge features. They use an older kernel base but backport security fixes and critical updates, providing enterprise stability while maintaining security. The kernel version number doesn’t reflect the actual security level.

What is kernel panic and how do I fix it?

Kernel panic occurs when the kernel encounters a fatal error it cannot recover from. To fix: boot into a previous kernel from GRUB, check logs with journalctl -b -1, remove problematic kernel, and investigate the root cause (often driver issues or hardware problems).

Should I use the mainline kernel or distribution kernel?

For most users, the distribution kernel is recommended as it’s tested, supported, and integrated with your distribution’s ecosystem. Use mainline kernels only if you need bleeding-edge features or specific hardware support not in your distribution kernel.

How can I build a custom kernel for my specific hardware?

Download kernel source from kernel.org, run make menuconfig to customize options, enable only drivers you need, compile with make -j$(nproc), and install with sudo make modules_install && sudo make install. This creates an optimized kernel but requires Linux experience.

What is the purpose of LTS (Long Term Support) kernels?

LTS kernels receive security updates and bug fixes for several years (typically 2-6 years) without major feature changes. They’re ideal for servers, embedded systems, and enterprise environments where stability is more important than new features.

Conclusion

Understanding how Linux kernel versions work and how different distributions handle kernel updates is essential for effective Linux system management. The 4.18 kernel brought significant improvements, but when and how it arrives on your system depends on your distribution’s philosophy and release cycle.

Enterprise distributions like RHEL prioritize stability with conservative kernel policies, while bleeding-edge distributions like Arch Linux deliver the latest kernels quickly. Choose your distribution and kernel update strategy based on your specific needs – whether that’s cutting-edge features, rock-solid stability, or freedom-focused principles.

Regular kernel updates are crucial for security and hardware support, but always test updates in non-production environments first. Keep multiple kernel versions installed as fallback options, and understand your distribution’s kernel management tools to maintain a healthy, secure Linux system.

Read More: https://www.networkworld.com