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 December 11, 1993 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. This filename can be absolute, or relative (which 68will resolve to the current working directory of the program 69generating it). Any sequence of 70.Em \&%N 71in this filename template will be replaced by the process name, 72.Em \&%P 73by the processes PID, and 74.Em \&%U 75by the UID. The name defaults to 76.Em \&%N.core , 77yielding the traditional 78.Fx 79behaviour. 80.Pp 81By default, a process that changes user or group credentials whether 82real or effective will not create a corefile. This behaviour can be 83changed to generate a core dump by setting the 84.Xr sysctl 8 85variable 86.Va kern.sugid_coredump 87to 1. 88.Pp 89The core file consists of the 90.Fa u . 91area, whose size (in pages) is 92defined by the 93.Dv UPAGES 94manifest in the 95.Aq Pa sys/param.h 96file. The 97.Fa u . 98area starts with a 99.Fa user 100structure as given in 101.Aq Pa sys/user.h . 102The remainder of the core 103file consists of the data pages followed by 104the stack pages of the process image. 105The amount of data space image in the core 106file is given (in pages) by the 107variable 108.Fa u_dsize 109in the 110.Fa u . 111area. 112The amount of stack image in the core file is given (in pages) by the 113variable 114.Fa u_ssize 115in the 116.Ar u . 117area. 118The size of a ``page'' is given by the constant 119.Dv PAGE_SIZE 120(also from 121.Aq Pa sys/param.h ) . 122.Sh EXAMPLES 123In order to store all core images in per-user private areas under 124.Pa /var/coredumps , 125the following 126.Xr sysctl 8 127command can be used: 128.Pp 129.Dl sysctl kern.corefile="/var/coredumps/\&%U/\&%N.core" 130.Sh SEE ALSO 131.Xr gdb 1 , 132.Xr kgdb 1 , 133.Xr setrlimit 2 , 134.Xr sigaction 2 , 135.Xr sysctl 8 136.Sh HISTORY 137A 138.Nm 139file format appeared in 140.At v6 . 141