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). 71.Pp 72The following format specifiers may be used in the 73.Va kern.corefile 74sysctl to insert additional information into the resulting core file 75name: 76.Bl -tag -width "1234567890" -compact -offset "12345" 77.It Em \&%H 78Machine hostname. 79.It Em \&%I 80An index starting at zero until the sysctl 81.Em debug.num_cores 82is reached. This can be useful for limiting the number of corefiles 83generated by a particular process. 84.It Em \&%N 85process name. 86.It Em \&%P 87processes PID. 88.It Em \&%U 89process UID. 90.El 91.Pp 92The name defaults to 93.Em \&%N.core , 94yielding the traditional 95.Fx 96behaviour. 97.Pp 98By default, a process that changes user or group credentials whether 99real or effective will not create a corefile. 100This behaviour can be 101changed to generate a core dump by setting the 102.Xr sysctl 8 103variable 104.Va kern.sugid_coredump 105to 1. 106.Pp 107Corefiles can be compressed by the kernel if the following items 108are included in the kernel configuration file: 109.Bl -tag -width "1234567890" -compact -offset "12345" 110.It options 111COMPRESS_USER_CORES 112.It devices 113gzio 114.El 115.Pp 116When COMPRESS_USER_CORES is included the following sysctls can control 117if core files will be compressed: 118.Bl -tag -width "kern.compress_user_cores_gzlevel" -compact -offset "12345" 119.It Em kern.compress_user_cores_gzlevel 120Gzip compression level. Defaults to -1. 121.It Em kern.compress_user_cores 122Actually compress user cores. Core files will have the suffix 123.Em .gz 124appended to them. 125.El 126.Sh EXAMPLES 127In order to store all core images in per-user private areas under 128.Pa /var/coredumps , 129the following 130.Xr sysctl 8 131command can be used: 132.Pp 133.Dl sysctl kern.corefile="/var/coredumps/\&%U/\&%N.core" 134.Sh SEE ALSO 135.Xr gdb 1 , 136.Xr kgdb 1 , 137.Xr setrlimit 2 , 138.Xr sigaction 2 , 139.Xr sysctl 8 140.Sh HISTORY 141A 142.Nm 143file format appeared in 144.At v6 . 145