The most complete, authoritative technical guide to the FreeBSD kernel’s i nternal structure has now been extensively updated to cover all major improvemen ts between Versions 5 and 11. Approximately one-third of this edition’s co ntent is completely new, and another one-third has been extensively rewritten.  Three long-time FreeBSD project leaders begin with a concise overview of the FreeBSD kernel’s current design and implementation. Next, they cover the FreeBSD kernel from the system-call level down–from the interface to t he kernel to the hardware. Explaining key design decisions, they detail the conc epts, data structures, and algorithms used in implementing each significant syst em facility, including process management, security, virtual memory, the I/O sys tem, filesystems, socket IPC, and networking. This Second Edition&nbs p;• Explains highly scalable and lightweight virtualization using FreeBSD jails, and virtual-machine acceleration with Xen and Virtio device paravirtuali zation • Describes new security features such as Capsicum sandboxi ng and GELI cryptographic disk protection • Fully covers NFSv4 and Open Solaris ZFS support • Introduces FreeBSD’s enhanced vo lume management and new journaled soft updates • Explains DTrace&r squo;s fine-grained process debugging/profiling • Reflects major i mprovements to networking, wireless, and USB support Readers can use th is guide as both a working reference and an in-depth study of a leading contempo rary, portable, open source operating system. Technical and sales support profes sionals will discover both FreeBSD’s capabilities and its limitations. App lications developers will learn how to effectively and efficiently interface wit h it; system administrators will learn how to maintain, tune, and configure it; and systems programmers will learn how to extend, enhance, and interface with it . Marshall Kirk McKusickwrites, consults, and teaches classes on UN IX- and BSD-related subjects. While at the University of California, Berkeley, h e implemented the 4.2BSD fast filesystem. He was research computer scientist at the Berkeley Computer Systems Research Group (CSRG), overseeing development and release of 4.3BSD and 4.4BSD. He is a FreeBSD Foundation board member and a long -time FreeBSD committer. Twice president of the Usenix Association, he is also a member of ACM, IEEE, and AAAS. George V. Neville-Neilhacks, writes , teaches, and consults on security, networking, and operating systems. A FreeBS D Foundation board member, he served on the FreeBSD Core Team for four years. Si nce 2004, he has written the “Kode Vicious” column forQueueand Communications of the ACM. He is vice chair of ACM’s Practitioner Board and a member of Usenix Association, ACM, IEEE, and AAAS. Robert N.M. Watsonis a University Lecturer in systems, security, and architecture in the S ecurity Research Group at the University of Cambridge Computer Laboratory. He su pervises advanced research in computer architecture, compilers, program analysis , operating systems, networking, and security. A FreeBSD Foundation board member , he served on the Core Team for ten years and has been a committer for fifteen years. He is a member of Usenix Association and ACM.