xv6 is a re-implementation of Dennis Ritchie's and Ken Thompson's Unix Version 6 (v6). xv6 loosely follows the structure and style of v6, but is implemented for a modern RISC-V multiprocessor using ANSI C. ACKNOWLEDGMENTS xv6 is inspired by John Lions's Commentary on UNIX 6th Edition (Peer to Peer Communications; ISBN: 1-57398-013-7; 1st edition (June 14, 2000)). See also https://pdos.csail.mit.edu/6.828/, which provides pointers to on-line resources for v6. The following people have made contributions: Russ Cox (context switching, locking), Cliff Frey (MP), Xiao Yu (MP), Nickolai Zeldovich, and Austin Clements. We are also grateful for the bug reports and patches contributed by Silas Boyd-Wickizer, Anton Burtsev, Dan Cross, Cody Cutler, Mike CAT, Tej Chajed, Asami Doi, eyalz800, , Nelson Elhage, Saar Ettinger, Alice Ferrazzi, Nathaniel Filardo, Peter Froehlich, Yakir Goaron,Shivam Handa, Bryan Henry, jaichenhengjie, Jim Huang, Alexander Kapshuk, Anders Kaseorg, kehao95, Wolfgang Keller, Jonathan Kimmitt, Eddie Kohler, Austin Liew, Imbar Marinescu, Yandong Mao, Matan Shabtay, Hitoshi Mitake, Carmi Merimovich, Mark Morrissey, mtasm, Joel Nider, Greg Price, Ayan Shafqat, Eldar Sehayek, Yongming Shen, Fumiya Shigemitsu, Takahiro, Cam Tenny, tyfkda, Rafael Ubal, Warren Toomey, Stephen Tu, Pablo Ventura, Xi Wang, Keiichi Watanabe, Nicolas Wolovick, wxdao, Grant Wu, Jindong Zhang, Icenowy Zheng, and Zou Chang Wei. The code in the files that constitute xv6 is Copyright 2006-2020 Frans Kaashoek, Robert Morris, and Russ Cox. ERROR REPORTS Please send errors and suggestions to Frans Kaashoek and Robert Morris (kaashoek,email@example.com). The main purpose of xv6 is as a teaching operating system for MIT's 6.S081, so we are more interested in simplifications and clarifications than new features. BUILDING AND RUNNING XV6 You will need a RISC-V "newlib" tool chain from https://github.com/riscv/riscv-gnu-toolchain, and qemu compiled for riscv64-softmmu. Once they are installed, and in your shell search path, you can run "make qemu".