Linux kernel internals and development
CPU affinity binds a process or thread to specific CPU cores, reducing cache misses, improving performance isolation, and managing NUMA locality. The sched_setaffinity() system call is the primary mechanism in Linux. Understanding how it works at the kernel level clarifies scheduler internals and helps you use it effectively. System Call Entry Point The sched_setaffinity() syscall…
You’re using a Linux-based OS right now, either directly or indirectly. But what do you actually call it? The naming question matters more than it seems — different distributions frame themselves differently, and understanding the terminology affects how you talk about infrastructure, apply for jobs, and read documentation. How Major Distributions Identify Themselves Red Hat…
The Linux kernel handles video mode configuration through bootloader parameters and kernel graphics drivers. Modern UEFI systems use Kernel Mode Setting (KMS) automatically, but you can override modes when needed. Legacy BIOS systems still use older mechanisms if you’re maintaining older hardware. UEFI Systems: Modern Video Mode Configuration On UEFI systems with GRUB2, add video…
Xen remains a production-grade hypervisor used by major cloud providers like AWS and Citrix, though KVM has become the default for most Linux distributions. This guide covers setting up Xen Domain-0 (the privileged management domain) on modern Fedora systems. Installing Xen Packages Install the required Xen packages: sudo dnf install xen xen-libs xen-runtime xen-dom0-tools Modern…
Static linking embeds all library code directly into your binary. On Linux, this sounds straightforward but glibc introduces complications that pure static binaries don’t truly exist — the C library still loads dynamic features at runtime like NSS (Name Service Switch), locale data, and character set converters. Understanding these constraints is essential before committing to…
Xen remains in production use at scale across AWS EC2, Citrix Hypervisor, and various cloud providers, though KVM has become the default hypervisor for most Linux distributions. If you’re operating a Xen environment, Dom0 resource management is critical to system stability. Why Dom0 Resource Management Matters Dom0 performance directly affects your entire virtualized infrastructure. Since…
The diff utility generates unified diffs that show changes between file versions. Always use the -u flag to create unified diffs, which are the standard format for patches. For a single file: diff -u original.c new.c > fix.patch For an entire directory tree: diff -rupN original/ new/ > patchfile.patch The flags break down as: -r:…
Modern Fedora (29+) uses firewalld by default instead of the legacy iptables service. If you’re working with an older system or one configured for iptables, the concepts here still apply, but you should first check what’s actually managing your firewall: systemctl status firewalld systemctl status iptables If firewalld is active, use firewall-cmd instead. For iptables-based…
Xen remains relevant for certain production workloads, particularly in cloud infrastructure (AWS EC2, Citrix Hypervisor) and enterprise environments requiring strong VM isolation. However, most Linux distributions now default to KVM for virtualization due to simpler setup and broader ecosystem support. If you’re evaluating hypervisors, consider KVM or container-based solutions like Podman and Kubernetes for new…
paravirt_ops is an abstraction layer in the Linux kernel that allows the same binary to run efficiently on both bare metal and various hypervisors through runtime patching. Rather than compiling separate kernels for each platform, paravirt_ops lets the kernel detect its environment at boot and optimize itself accordingly. The Core Problem paravirt_ops Solves Traditional virtualization…
This post covers Xen virtualization benchmarks from 2013. While Xen remains in production use (AWS EC2, Citrix Hypervisor), KVM has become the default hypervisor for most Linux distributions. For current production environments, evaluate KVM with libvirt, direct container solutions (Docker, Kubernetes), or cloud-native platforms. This post is preserved for historical reference and understanding legacy Xen…
Xen remains a production-grade hypervisor used in enterprise environments (AWS EC2, Citrix Hypervisor), though KVM has become the default for most Linux distributions. This guide covers building a stable Xen Dom0 on current Fedora releases using modern kernel sources. Hardware Considerations This guide assumes server-class hardware with: Intel or AMD processor with virtualization extensions (VT-x…
Xen remains relevant in production environments (AWS EC2, Citrix Hypervisor), though KVM has become the default for most Linux distributions. This guide covers frequent installation and configuration issues specific to Fedora Dom0 setups, with many tips applicable to other Linux platforms. BIOS Configuration If Xen fails with “I/O virtualization disabled,” you need to enable virtualization…
Xen remains a critical hypervisor in production environments—AWS EC2, Citrix Hypervisor, and other cloud platforms rely on it—but most Linux distributions now default to KVM for general-purpose virtualization. If you’re working with Xen specifically, this guide covers Dom0 and DomU setup on modern distributions. When to Use Xen Xen is worth considering if you need:…
To find all available versions of a package in your repository, use the –showduplicates flag: dnf list –showduplicates kernel Or for other packages: dnf list –showduplicates <package-name> The output shows both installed and available versions with their release tags. For example: Installed Packages kernel.x86_64 6.8.1-1.fc39 @updates Available Packages kernel.x86_64 6.7.12-200.fc39 updates kernel.x86_64 6.6.25-1.fc39 updates kernel.x86_64…
Port forwarding allows external hosts to reach services inside a private network by mapping traffic from a public address to an internal one. On Linux, this is implemented through iptables rules that modify packet headers as they traverse the kernel’s netfilter framework. Common use cases include exposing HTTP/HTTPS servers from a private LAN to the…
On Fedora/RHEL-based systems: dnf install ecryptfs-utils On Debian/Ubuntu: apt-get install ecryptfs-utils Load the kernel module modprobe ecryptfs To ensure the module loads automatically on boot, add it to /etc/modules-load.d/: echo “ecryptfs” | sudo tee /etc/modules-load.d/ecryptfs.conf Create directories You’ll need two directories: one for encrypted storage (.private) and one as the mount point (private). The .private…
Xen remains a production hypervisor for enterprise deployments (AWS EC2, Citrix Hypervisor), though KVM has become the default for most Linux distributions. If you’re deploying Xen in 2026, you’ll likely be working with recent stable releases rather than the legacy versions covered in older guides. This guide covers building a modern Xen Dom0 environment on…
This article documents performance benchmarks for Xen virtualization, comparing CPU and memory performance between Dom0 (privileged domain), DomU (unprivileged guest), and bare metal. While Xen remains in production use (AWS EC2, Citrix Hypervisor, Oracle Cloud), most Linux distributions default to KVM for new deployments. For contemporary virtualization needs, evaluate both Xen and KVM based on…