Second Distribution of Berkeley PDP-11 Software for UNIX Release 2.9 (revised June 1983) A new release of the UNIX system with many enhancements is available from the Computer Science Division of the University of California at Berkeley. It is a complete V7 UNIX system, including the kernel, all standard utilities, and additional Berkeley products. The kernel will run on any PDP-II with memory management hardware and at least 192K bytes of memory, including the 11/23, 11/24, 11/34, 11/34A, 11/40, 11/44, 11/45, 11/55, and 11/70. It supports most common disks (RK05/06/07, RL01/02, RM02/03/05, RP03/04/05/06, and emulations of these) and tapes (TM02/03, TM 11, and TS 11). With only a few exceptions (pcc and INGRES), all of the programs in the release will also run on all of the supported machines. The major kernel changes since the 2.8BSD distribution are: Process control, a mechanism for stopping and restarting jobs in foreground or background, and the new reliable signal mechanism that supports it. This is nearly identical to the process control facility of 4.1BSD VMUNIX (the Berkeley VAX UNIX system). Vfork, a more efficient version of fork. Automatic reboots, after crashes or on demand. Automatic detection of hardware configuration at boot time, with most of the configuration-dependent addresses and vectors in a single ASCII file. Much easier kernel configuration process, with most parameters in one machine description file. There are numerous efficiency changes. System overhead has markedly decreased in a number of areas: floating point traps (90% decrease) overlay switches (45% decrease), and system calls (22% decrease). There have been many bug fixes. The system is now far more robust. Other features of the kernel, which were also in the 2.8BSD release, include hashing buffers and inodes, moving buffers and clists out of kernel data space, and the 1K block filesystem. The system supports kernel overlays, allowing it to run on nonseparate I/D machines. It also supports user overlays, so that ex version 3 can be run, even on nonseparate machines! The Berkeley tty driver is included; it correctly handles erase and kill characters on crt and printing terminals, including correctly backspacing over tabs and control characters. The enhanced Berkeley implementation of the TCP/IP network facility is included. Changes to the kernel are conditionally compiled with mnemonic names, making it easy to turn on and off features you decide you do or do not want. This kernel contains contributions from Berkeley's Computer Systems Research Group, the U.S. Geological Survey system, DEC's UNIX Engineering Group, and Tektronix (to mention only a few). This package also includes the instructional Pascal system, the editor ex, the INGRES database management system, and other software (some of which is described below). Source code, binaries and machine readable versions of all documentation are included. The distribution is provided on two 9-track 800BPI magnetic tapes, one of which is bootable and contains the standalone utilities required to bring up a root filesystem and the kernel. The remainder of the sources, documentation and binaries are in tar format, blocked by a factor of 20 (1024.0 byte records). Tapes written at 1600BPI are available, as are tapes intended for use on the DEC TS-11 tape drive. We will supply the magnetic tape(s) on which the software will be written. Distributions of the software on disk media are not available. Tp and cpio formats are also not available. ___ DEC, PDP, and VAX are trademarks of Digital Equipment Corporation. UNIX is a trademark of Bell Laboratories.