Linux Kernel

The Linux Kernel is the core of the Linux operating system, originally created by Linus Torvalds in 1991 and now developed by thousands of contributors worldwide. As of 2026, the Linux kernel consists of over 30 million lines of code, with over 15,000 unique contributors, and receives over 10,000 commits per release cycle (roughly every 9-10 weeks). The kernel powers an estimated 96% of the top 1 million web servers, all Android devices (over 3 billion active), all Chromebooks, the entire top 500 supercomputer list, most IoT devices, and critical infrastructure worldwide. Key architectural features include: monolithic kernel design with loadable kernel modules (LKMs) for dynamic functionality, preemptive multitasking with the Completely Fair Scheduler (CFS, replaced by EEVDF in 6.6+), virtual memory management with demand paging and swap, the ext4, Btrfs, XFS, and ZFS filesystems, the block I/O layer with multi-queue (blk-mq) for NVMe performance, the network stack (TCP/IP, UDP, IPv4/IPv6, Netfilter/iptables/nftables firewall, eBPF for programmable packet processing), device drivers for virtually every hardware device (over 25,000 drivers), support for over 30 CPU architectures (x86, x86-64, ARM, ARM64, RISC-V, MIPS, PowerPC, SPARC, s390x), power management (CPU frequency scaling, suspend to RAM/disk, runtime PM), security modules (SELinux, AppArmor, SMACK, and Landlock), kernel namespaces and cgroups for container isolation (the foundation of Docker and Kubernetes), KVM for hardware virtualization, and the DKMS infrastructure for out-of-tree module building.