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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)core.5 8.3 (Berkeley) 12/11/93 33.\" $FreeBSD$ 34.\" 35.Dd January 9, 2002 36.Dt CORE 5 37.Os 38.Sh NAME 39.Nm core 40.Nd memory image file format 41.Sh SYNOPSIS 42.In sys/param.h 43.Sh DESCRIPTION 44A small number of signals which cause abnormal termination of a process 45also cause a record of the process's in-core state to be written 46to disk for later examination by one of the available debuggers. 47(See 48.Xr sigaction 2 . ) 49This memory image is written to a file named by default 50.Nm programname.core 51in the working directory; 52provided the terminated process had write permission in the directory, 53and provided the abnormality did not cause 54a system crash. 55(In this event, the decision to save the core file is arbitrary, see 56.Xr savecore 8 . ) 57.Pp 58The maximum size of a core file is limited by 59.Xr setrlimit 2 . 60Files which would be larger than the limit are not created. 61.Pp 62The name of the file is controlled via the 63.Xr sysctl 8 64variable 65.Va kern.corefile . 66The contents of this variable describes a filename to store 67the core image to. 68This filename can be absolute, or relative (which 69will resolve to the current working directory of the program 70generating it). 71Any sequence of 72.Em \&%N 73in this filename template will be replaced by the process name, 74.Em \&%P 75by the processes PID, and 76.Em \&%U 77by the UID. 78The name defaults to 79.Em \&%N.core , 80yielding the traditional 81.Fx 82behaviour. 83.Pp 84By default, a process that changes user or group credentials whether 85real or effective will not create a corefile. 86This behaviour can be 87changed to generate a core dump by setting the 88.Xr sysctl 8 89variable 90.Va kern.sugid_coredump 91to 1. 92.Pp 93The core file consists of the 94.Fa u. 95area, whose size (in pages) is 96defined by the 97.Dv UPAGES 98manifest in the 99.In sys/param.h 100file. 101The 102.Fa u. 103area starts with a 104.Fa user 105structure as given in 106.In sys/user.h . 107The remainder of the core 108file consists of the data pages followed by 109the stack pages of the process image. 110The amount of data space image in the core 111file is given (in pages) by the 112variable 113.Fa u_dsize 114in the 115.Fa u. 116area. 117The amount of stack image in the core file is given (in pages) by the 118variable 119.Fa u_ssize 120in the 121.Fa u. 122area. 123The size of a ``page'' is given by the constant 124.Dv PAGE_SIZE 125(also from 126.In sys/param.h ) . 127.Sh EXAMPLES 128In order to store all core images in per-user private areas under 129.Pa /var/coredumps , 130the following 131.Xr sysctl 8 132command can be used: 133.Pp 134.Dl sysctl kern.corefile="/var/coredumps/\&%U/\&%N.core" 135.Sh SEE ALSO 136.Xr gdb 1 , 137.Xr kgdb 1 , 138.Xr setrlimit 2 , 139.Xr sigaction 2 , 140.Xr sysctl 8 141.Sh HISTORY 142A 143.Nm 144file format appeared in 145.At v6 . 146