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 November 22, 2012 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.ncores 82is reached. 83This can be useful for limiting the number of corefiles 84generated by a particular process. 85.It Em \&%N 86process name. 87.It Em \&%P 88processes PID. 89.It Em \&%U 90process UID. 91.El 92.Pp 93The name defaults to 94.Em \&%N.core , 95yielding the traditional 96.Fx 97behaviour. 98.Pp 99By default, a process that changes user or group credentials whether 100real or effective will not create a corefile. 101This behaviour can be 102changed to generate a core dump by setting the 103.Xr sysctl 8 104variable 105.Va kern.sugid_coredump 106to 1. 107.Pp 108Corefiles can be compressed by the kernel if the following items 109are included in the kernel configuration file: 110.Bl -tag -width "1234567890" -compact -offset "12345" 111.It options 112COMPRESS_USER_CORES 113.It devices 114gzio 115.El 116.Pp 117When COMPRESS_USER_CORES is included the following sysctls can control 118if core files will be compressed: 119.Bl -tag -width "kern.compress_user_cores_gzlevel" -compact -offset "12345" 120.It Em kern.compress_user_cores_gzlevel 121Gzip compression level. 122Defaults to -1. 123.It Em kern.compress_user_cores 124Actually compress user cores. 125Core files will have the suffix 126.Em .gz 127appended to them. 128.El 129.Sh EXAMPLES 130In order to store all core images in per-user private areas under 131.Pa /var/coredumps , 132the following 133.Xr sysctl 8 134command can be used: 135.Pp 136.Dl sysctl kern.corefile=/var/coredumps/\&%U/\&%N.core 137.Sh SEE ALSO 138.Xr gdb 1 , 139.Xr kgdb 1 , 140.Xr setrlimit 2 , 141.Xr sigaction 2 , 142.Xr sysctl 8 143.Sh HISTORY 144A 145.Nm 146file format appeared in 147.At v6 . 148