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core(5) [bsd man page]

CORE(5) 							File Formats Manual							   CORE(5)

NAME
core - format of memory image file SYNOPSIS
#include <sys/param.h> DESCRIPTION
The UNIX System writes out a memory image of a terminated process when any of various errors occur. See sigvec(2) for the list of reasons; the most common are memory violations, illegal instructions, bus errors, and user-generated quit signals. The memory image is called `core' and is written in the process's working directory (provided it can be; normal access controls apply). The core file consists of the u. area, whose size (in 64 byte `clicks') is defined by the USIZE manifest in the <sys/param.h> file. The u. area starts with a user structure as given in <sys/user.h>. The rest of the u. area consists of the kernel stack for the terminated process which includes (among other things) the processor registers at the time of the fault; see the system listings for the format of this area. The remainder of the core file consists first of the data pages and then the stack pages of the process image. The amount of data space image in the core file is given (in clicks) by the variable u_dsize in the u. area. If the text segment was not write-only and and shared it is included as the first etext bytes of the data image where etext is taken from the symbol table of the object file which generated the memory image. The amount of stack image in the core file is given (in clicks) by the variable u_ssize in the u. area. In general the debugger adb(1) is sufficient to deal with core images. SEE ALSO
adb(1), sigvec(2), stack(5) 3rd Berkeley Distribution January 26, 1987 CORE(5)

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CORE(5) 						      BSD File Formats Manual							   CORE(5)

NAME
core -- memory image file format SYNOPSIS
#include <sys/param.h> DESCRIPTION
A small number of signals which cause abnormal termination of a process also cause a record of the process's in-core state to be written to disk for later examination by one of the available debuggers. (See sigaction(2).) This memory image is written to a file named by default programname.core in the working directory; provided the terminated process had write permission in the directory, and provided the abnormal- ity did not cause a system crash. (In this event, the decision to save the core file is arbitrary, see savecore(8).) The maximum size of a core file is limited by setrlimit(2). Files which would be larger than the limit are not created. The name of the file is controlled via the sysctl(8) variable kern.corefile. The contents of this variable describes a filename to store the core image to. This filename can be absolute, or relative (which will resolve to the current working directory of the program generating it). The following format specifiers may be used in the kern.corefile sysctl to insert additional information into the resulting core file name: %H Machine hostname. %I An index starting at zero until the sysctl debug.ncores is reached. This can be useful for limiting the number of corefiles generated by a particular process. %N process name. %P processes PID. %U process UID. The name defaults to %N.core, yielding the traditional FreeBSD behaviour. By default, a process that changes user or group credentials whether real or effective will not create a corefile. This behaviour can be changed to generate a core dump by setting the sysctl(8) variable kern.sugid_coredump to 1. Corefiles can be compressed by the kernel if the following items are included in the kernel configuration file: options COMPRESS_USER_CORES devices gzio When COMPRESS_USER_CORES is included the following sysctls can control if core files will be compressed: kern.compress_user_cores_gzlevel Gzip compression level. Defaults to -1. kern.compress_user_cores Actually compress user cores. Core files will have the suffix .gz appended to them. EXAMPLES
In order to store all core images in per-user private areas under /var/coredumps, the following sysctl(8) command can be used: sysctl kern.corefile=/var/coredumps/%U/%N.core SEE ALSO
gdb(1), kgdb(1), setrlimit(2), sigaction(2), sysctl(8) HISTORY
A core file format appeared in Version 6 AT&T UNIX. BSD
November 22, 2012 BSD

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