1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)core.5 8.3 (Berkeley) 12/11/93 29.\" $FreeBSD: src/share/man/man5/core.5,v 1.8.2.5 2003/01/07 22:03:50 keramida Exp $ 30.\" $DragonFly: src/share/man/man5/core.5,v 1.4 2006/05/26 19:39:40 swildner Exp $ 31.\" 32.Dd January 9, 2002 33.Dt CORE 5 34.Os 35.Sh NAME 36.Nm core 37.Nd memory image file format 38.Sh SYNOPSIS 39.In sys/param.h 40.Sh DESCRIPTION 41A small number of signals which cause abnormal termination of a process 42also cause a record of the process's in-core state to be written 43to disk for later examination by one of the available debuggers. 44(See 45.Xr sigaction 2 . ) 46This memory image is written to a file named by default 47.Nm programname.core 48in the working directory; 49provided the terminated process had write permission in the directory, 50and provided the abnormality did not cause 51a system crash. 52(In this event, the decision to save the core file is arbitrary, see 53.Xr savecore 8 . ) 54.Pp 55The maximum size of a core file is limited by 56.Xr setrlimit 2 . 57Files which would be larger than the limit are not created. 58.Pp 59The name of the file is controlled via the 60.Xr sysctl 8 61variable 62.Va kern.corefile . 63The contents of this variable describes a filename to store 64the core image to. 65This filename can be absolute, or relative (which 66will resolve to the current working directory of the program 67generating it). 68Any sequence of 69.Em \&%N 70in this filename template will be replaced by the process name, 71.Em \&%P 72by the processes PID, and 73.Em \&%U 74by the UID. 75The name defaults to 76.Em \&%N.core , 77yielding the traditional 78.Dx 79behaviour. 80.Pp 81By default, a process that changes user or group credentials whether 82real or effective will not create a corefile. 83This behaviour can be 84changed to generate a core dump by setting the 85.Xr sysctl 8 86variable 87.Va kern.sugid_coredump 88to 1. 89.Pp 90The core file consists of the 91.Fa u. 92area, whose size (in pages) is 93defined by the 94.Dv UPAGES 95manifest in the 96.In sys/param.h 97file. 98The 99.Fa u. 100area starts with a 101.Fa user 102structure as given in 103.In sys/user.h . 104The remainder of the core 105file consists of the data pages followed by 106the stack pages of the process image. 107The amount of data space image in the core 108file is given (in pages) by the 109variable 110.Fa u_dsize 111in the 112.Fa u. 113area. 114The amount of stack image in the core file is given (in pages) by the 115variable 116.Fa u_ssize 117in the 118.Fa u. 119area. 120The size of a ``page'' is given by the constant 121.Dv PAGE_SIZE 122(also from 123.In sys/param.h ) . 124.Sh EXAMPLES 125In order to store all core images in per-user private areas under 126.Pa /var/coredumps , 127the following 128.Xr sysctl 8 129command can be used: 130.Pp 131.Dl sysctl kern.corefile="/var/coredumps/\&%U/\&%N.core" 132.Sh SEE ALSO 133.Xr gdb 1 , 134.Xr kgdb 1 , 135.Xr setrlimit 2 , 136.Xr sigaction 2 , 137.Xr sysctl 8 138.Sh HISTORY 139A 140.Nm 141file format appeared in 142.At v6 . 143