+++ /dev/null
-.\" Copyright (c) 2006, 2008 by Michael Kerrisk <mtk.manpages@gmail.com>
-.\"
-.\" %%%LICENSE_START(VERBATIM)
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\" %%%LICENSE_END
-.\"
-.TH CORE 5 2014-08-19 "Linux" "Linux Programmer's Manual"
-.SH NAME
-core \- core dump file
-.SH DESCRIPTION
-The default action of certain signals is to cause a process to terminate
-and produce a
-.IR "core dump file" ,
-a disk file containing an image of the process's memory at
-the time of termination.
-This image can be used in a debugger (e.g.,
-.BR gdb (1))
-to inspect the state of the program at the time that it terminated.
-A list of the signals which cause a process to dump core can be found in
-.BR signal (7).
-
-A process can set its soft
-.B RLIMIT_CORE
-resource limit to place an upper limit on the size of the core dump file
-that will be produced if it receives a "core dump" signal; see
-.BR getrlimit (2)
-for details.
-
-There are various circumstances in which a core dump file is
-not produced:
-.IP * 3
-The process does not have permission to write the core file.
-(By default, the core file is called
-.IR core
-or
-.IR core.pid ,
-where
-.I pid
-is the ID of the process that dumped core,
-and is created in the current working directory.
-See below for details on naming.)
-Writing the core file will fail if the directory in which
-it is to be created is nonwritable,
-or if a file with the same name exists and
-is not writable
-or is not a regular file
-(e.g., it is a directory or a symbolic link).
-.IP *
-A (writable, regular) file with the same name as would be used for the
-core dump already exists, but there is more than one hard link to that
-file.
-.IP *
-The filesystem where the core dump file would be created is full;
-or has run out of inodes; or is mounted read-only;
-or the user has reached their quota for the filesystem.
-.IP *
-The directory in which the core dump file is to be created does
-not exist.
-.IP *
-The
-.B RLIMIT_CORE
-(core file size) or
-.B RLIMIT_FSIZE
-(file size) resource limits for the process are set to zero; see
-.BR getrlimit (2)
-and the documentation of the shell's
-.I ulimit
-command
-.RI ( limit
-in
-.BR csh (1)).
-.IP *
-The binary being executed by the process does not have read
-permission enabled.
-.IP *
-The process is executing a set-user-ID (set-group-ID) program
-that is owned by a user (group) other than the real user (group)
-ID of the process.
-(However, see the description of the
-.BR prctl (2)
-.B PR_SET_DUMPABLE
-operation, and the description of the
-.I /proc/sys/fs/suid_dumpable
-.\" FIXME . Perhaps relocate discussion of /proc/sys/fs/suid_dumpable
-.\" and PR_SET_DUMPABLE to this page?
-file in
-.BR proc (5).)
-.IP *
-(Since Linux 3.7)
-.\" commit 046d662f481830e652ac34cd112249adde16452a
-The kernel was configured without the
-.BR CONFIG_COREDUMP
-option.
-.PP
-In addition,
-a core dump may exclude part of the address space of the process if the
-.BR madvise (2)
-.B MADV_DONTDUMP
-flag was employed.
-.SS Naming of core dump files
-By default, a core dump file is named
-.IR core ,
-but the
-.I /proc/sys/kernel/core_pattern
-file (since Linux 2.6 and 2.4.21)
-can be set to define a template that is used to name core dump files.
-The template can contain % specifiers which are substituted
-by the following values when a core file is created:
-.PP
-.RS 4
-.PD 0
-.TP 4
-%%
-a single % character
-.TP
-%c
-core file size soft resource limit of crashing process (since Linux 2.6.24)
-.TP
-%d
-.\" Added in git commit 12a2b4b2241e318b4f6df31228e4272d2c2968a1
-dump mode\(emsame as value returned by
-.BR prctl (2)
-.B PR_GET_DUMPABLE
-(since Linux 3.7)
-.TP
-%e
-executable filename (without path prefix)
-.TP
-%E
-pathname of executable,
-with slashes (\(aq/\(aq) replaced by exclamation marks (\(aq!\(aq)
-(since Linux 3.0).
-.TP
-%g
-(numeric) real GID of dumped process
-.TP
-%h
-hostname (same as \fInodename\fP returned by \fBuname\fP(2))
-.TP
-%p
-PID of dumped process,
-as seen in the PID namespace in which the process resides
-.TP
-%P
-.\" Added in git commit 65aafb1e7484b7434a0c1d4c593191ebe5776a2f
-PID of dumped process, as seen in the initial PID namespace
-(since Linux 3.12)
-.TP
-%s
-number of signal causing dump
-.TP
-%t
-time of dump, expressed as seconds since the
-Epoch, 1970-01-01 00:00:00 +0000 (UTC)
-.TP
-%u
-(numeric) real UID of dumped process
-.PD
-.RE
-.PP
-A single % at the end of the template is dropped from the
-core filename, as is the combination of a % followed by any
-character other than those listed above.
-All other characters in the template become a literal
-part of the core filename.
-The template may include \(aq/\(aq characters, which are interpreted
-as delimiters for directory names.
-The maximum size of the resulting core filename is 128 bytes (64 bytes
-in kernels before 2.6.19).
-The default value in this file is "core".
-For backward compatibility, if
-.I /proc/sys/kernel/core_pattern
-does not include "%p" and
-.I /proc/sys/kernel/core_uses_pid
-(see below)
-is nonzero, then .PID will be appended to the core filename.
-
-Since version 2.4, Linux has also provided
-a more primitive method of controlling
-the name of the core dump file.
-If the
-.I /proc/sys/kernel/core_uses_pid
-file contains the value 0, then a core dump file is simply named
-.IR core .
-If this file contains a nonzero value, then the core dump file includes
-the process ID in a name of the form
-.IR core.PID .
-
-Since Linux 3.6,
-.\" 9520628e8ceb69fa9a4aee6b57f22675d9e1b709
-if
-.I /proc/sys/fs/suid_dumpable
-is set to 2 ("suidsafe"), the pattern must be either an absolute pathname
-(starting with a leading \(aq/\(aq character) or a pipe, as defined below.
-.SS Piping core dumps to a program
-Since kernel 2.6.19, Linux supports an alternate syntax for the
-.I /proc/sys/kernel/core_pattern
-file.
-If the first character of this file is a pipe symbol (\fB|\fP),
-then the remainder of the line is interpreted as a program to be
-executed.
-Instead of being written to a disk file, the core dump is given as
-standard input to the program.
-Note the following points:
-.IP * 3
-The program must be specified using an absolute pathname (or a
-pathname relative to the root directory, \fI/\fP),
-and must immediately follow the '|' character.
-.IP *
-The process created to run the program runs as user and group
-.IR root .
-.IP *
-Command-line arguments can be supplied to the
-program (since Linux 2.6.24),
-delimited by white space (up to a total line length of 128 bytes).
-.IP *
-The command-line arguments can include any of
-the % specifiers listed above.
-For example, to pass the PID of the process that is being dumped, specify
-.I %p
-in an argument.
-.SS Controlling which mappings are written to the core dump
-Since kernel 2.6.23, the Linux-specific
-.IR /proc/PID/coredump_filter
-file can be used to control which memory segments are written to the
-core dump file in the event that a core dump is performed for the
-process with the corresponding process ID.
-
-The value in the file is a bit mask of memory mapping types (see
-.BR mmap (2)).
-If a bit is set in the mask, then memory mappings of the
-corresponding type are dumped; otherwise they are not dumped.
-The bits in this file have the following meanings:
-.PP
-.PD 0
-.RS 4
-.TP
-bit 0
-Dump anonymous private mappings.
-.TP
-bit 1
-Dump anonymous shared mappings.
-.TP
-bit 2
-Dump file-backed private mappings.
-.TP
-bit 3
-Dump file-backed shared mappings.
-.\" file-backed shared mappings of course also update the underlying
-.\" mapped file.
-.TP
-bit 4 (since Linux 2.6.24)
-Dump ELF headers.
-.TP
-bit 5 (since Linux 2.6.28)
-Dump private huge pages.
-.TP
-bit 6 (since Linux 2.6.28)
-Dump shared huge pages.
-.RE
-.PD
-.PP
-By default, the following bits are set: 0, 1, 4 (if the
-.B CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS
-kernel configuration option is enabled), and 5.
-The value of this file is displayed in hexadecimal.
-(The default value is thus displayed as 33.)
-
-Memory-mapped I/O pages such as frame buffer are never dumped, and
-virtual DSO pages are always dumped, regardless of the
-.I coredump_filter
-value.
-
-A child process created via
-.BR fork (2)
-inherits its parent's
-.I coredump_filter
-value;
-the
-.I coredump_filter
-value is preserved across an
-.BR execve (2).
-
-It can be useful to set
-.I coredump_filter
-in the parent shell before running a program, for example:
-
-.in +4n
-.nf
-.RB "$" " echo 0x7 > /proc/self/coredump_filter"
-.RB "$" " ./some_program"
-.fi
-.in
-.PP
-This file is provided only if the kernel was built with the
-.B CONFIG_ELF_CORE
-configuration option.
-.SH NOTES
-The
-.BR gdb (1)
-.I gcore
-command can be used to obtain a core dump of a running process.
-
-In Linux versions up to and including 2.6.27,
-.\" Changed with commit 6409324b385f3f63a03645b4422e3be67348d922
-if a multithreaded process (or, more precisely, a process that
-shares its memory with another process by being created with the
-.B CLONE_VM
-flag of
-.BR clone (2))
-dumps core, then the process ID is always appended to the core filename,
-unless the process ID was already included elsewhere in the
-filename via a %p specification in
-.IR /proc/sys/kernel/core_pattern .
-(This is primarily useful when employing the obsolete
-LinuxThreads implementation,
-where each thread of a process has a different PID.)
-.\" Always including the PID in the name of the core file made
-.\" sense for LinuxThreads, where each thread had a unique PID,
-.\" but doesn't seem to serve any purpose with NPTL, where all the
-.\" threads in a process share the same PID (as POSIX.1 requires).
-.\" Probably the behavior is maintained so that applications using
-.\" LinuxThreads continue appending the PID (the kernel has no easy
-.\" way of telling which threading implementation the user-space
-.\" application is using). -- mtk, April 2006
-.SH EXAMPLE
-The program below can be used to demonstrate the use of the
-pipe syntax in the
-.I /proc/sys/kernel/core_pattern
-file.
-The following shell session demonstrates the use of this program
-(compiled to create an executable named
-.IR core_pattern_pipe_test ):
-.PP
-.in +4n
-.nf
-.RB "$" " cc \-o core_pattern_pipe_test core_pattern_pipe_test.c"
-.RB "$" " su"
-Password:
-.RB "#" " echo \(dq|$PWD/core_pattern_pipe_test %p \
-UID=%u GID=%g sig=%s\(dq > \e"
-.B " /proc/sys/kernel/core_pattern"
-.RB "#" " exit"
-.RB "$" " sleep 100"
-.BR "^\e" " # type control-backslash"
-Quit (core dumped)
-.RB "$" " cat core.info"
-argc=5
-argc[0]=</home/mtk/core_pattern_pipe_test>
-argc[1]=<20575>
-argc[2]=<UID=1000>
-argc[3]=<GID=100>
-argc[4]=<sig=3>
-Total bytes in core dump: 282624
-.fi
-.in
-.SS Program source
-\&
-.nf
-/* core_pattern_pipe_test.c */
-
-#define _GNU_SOURCE
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <limits.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-
-#define BUF_SIZE 1024
-
-int
-main(int argc, char *argv[])
-{
- int tot, j;
- ssize_t nread;
- char buf[BUF_SIZE];
- FILE *fp;
- char cwd[PATH_MAX];
-
- /* Change our current working directory to that of the
- crashing process */
-
- snprintf(cwd, PATH_MAX, "/proc/%s/cwd", argv[1]);
- chdir(cwd);
-
- /* Write output to file "core.info" in that directory */
-
- fp = fopen("core.info", "w+");
- if (fp == NULL)
- exit(EXIT_FAILURE);
-
- /* Display command\-line arguments given to core_pattern
- pipe program */
-
- fprintf(fp, "argc=%d\\n", argc);
- for (j = 0; j < argc; j++)
- fprintf(fp, "argc[%d]=<%s>\\n", j, argv[j]);
-
- /* Count bytes in standard input (the core dump) */
-
- tot = 0;
- while ((nread = read(STDIN_FILENO, buf, BUF_SIZE)) > 0)
- tot += nread;
- fprintf(fp, "Total bytes in core dump: %d\\n", tot);
-
- fclose(fp);
- exit(EXIT_SUCCESS);
-}
-.fi
-.SH SEE ALSO
-.BR bash (1),
-.BR gdb (1),
-.BR getrlimit (2),
-.BR mmap (2),
-.BR prctl (2),
-.BR sigaction (2),
-.BR elf (5),
-.BR proc (5),
-.BR pthreads (7),
-.BR signal (7)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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