xv6 is a re-implementation of Dennis Ritchie's and Ken Thompson's UnixVersion 6 (v6).  xv6 loosely follows the structure and style of v6,but is implemented for a modern RISC-V multiprocessor using ANSI C.ACKNOWLEDGMENTSxv6 is inspired by John Lions's Commentary on UNIX 6th Edition (Peerto Peer Communications; ISBN: 1-57398-013-7; 1st edition (June 14,2000)).  See alsohttps://pdos.csail.mit.edu/6.1810/, which providespointers 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 AustinClements.We are also grateful for the bug reports and patches contributed byTakahiro Aoyagi, Marcelo Arroyo, Silas Boyd-Wickizer, Anton Burtsev,carlclone, Ian Chen, Dan Cross, Cody Cutler, Mike CAT, Tej Chajed,Asami Doi,Wenyang Duan, eyalz800, Nelson Elhage, Saar Ettinger, AliceFerrazzi, Nathaniel Filardo, flespark, Peter Froehlich, Yakir Goaron,Shivam Handa, Matt Harvey, Bryan Henry, jaichenhengjie, Jim Huang,Matúš Jókay, John Jolly, Alexander Kapshuk, Anders Kaseorg, kehao95,Wolfgang Keller, Jungwoo Kim, Jonathan Kimmitt, Eddie Kohler, VadimKolontsov, Austin Liew, l0stman, Pavan Maddamsetti, Imbar Marinescu,Yandong Mao, Matan Shabtay, Hitoshi Mitake, Carmi Merimovich, MarkMorrissey, mtasm, Joel Nider, Hayato Ohhashi, OptimisticSide,phosphagos, Harry Porter, Greg Price, RayAndrew, Jude Rich, segfault,Ayan Shafqat, Eldar Sehayek, Yongming Shen, Fumiya Shigemitsu, snoire,Taojie, Cam Tenny, tyfkda, Warren Toomey, Stephen Tu, Alissa Tung,Rafael Ubal, Amane Uehara, Pablo Ventura, Xi Wang, WaheedHafez,Keiichi Watanabe, Lucas Wolf, Nicolas Wolovick, wxdao, Grant Wu, x653,Jindong Zhang, Icenowy Zheng, ZhUyU1997, and Zou Chang Wei.ERROR REPORTSPlease send errors and suggestions to Frans Kaashoek and Robert Morris(kaashoek,rtm@mit.edu).  The main purpose of xv6 is as a teachingoperating system for MIT's 6.1810, so we are more interested insimplifications and clarifications than new features.BUILDING AND RUNNING XV6You will need a RISC-V "newlib" tool chain fromhttps://github.com/riscv/riscv-gnu-toolchain, and qemu compiled forriscv64-softmmu.  Once they are installed, and in your shellsearch path, you can run "make qemu".