프로그램 구현 문제로 서버가 죽었을 경우 core가 떨구어, 디버깅 할때 유용하게 사용이 되고 있습니다.
허지만 코어파일들이 많아 지고, 여러 개의 서버를 프로그램을 하나의 머신에 서비스하는 경우에는
현재는 알 수 있지만, 시간이 지나면 알 수 없는 문제를 가지고 있습니다. 이러한 문제를 해결하기 위해서는
어떤 서버에서 코어 파일이 생성되었고, 프로세스 시간등을 파일 이름에 기록해 놓는 다면 관리적인
측면에서 유용하지 않을까 하는 생각에서 정리 해봤습니다.
먼저 man 에 있는 내용을 보시면,
영구적으로 세팅하기 위해서는 다음과 같이 수정하시면 됩니다.
vi /etc/sysctl.conf
kernel.core_pattern = [ path ]/core/%e-%t-%p.core
수정후,
sysctl -p
패턴 확인하는 방법은
허지만 코어파일들이 많아 지고, 여러 개의 서버를 프로그램을 하나의 머신에 서비스하는 경우에는
현재는 알 수 있지만, 시간이 지나면 알 수 없는 문제를 가지고 있습니다. 이러한 문제를 해결하기 위해서는
어떤 서버에서 코어 파일이 생성되었고, 프로세스 시간등을 파일 이름에 기록해 놓는 다면 관리적인
측면에서 유용하지 않을까 하는 생각에서 정리 해봤습니다.
먼저 man 에 있는 내용을 보시면,
NAME
core - core dump file
DESCRIPTION
The default action of certain signals is to cause a process to terminate and produce a 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., 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
signal(7).
A process can set its soft 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 getrlimit(2) for details.
There are various circumstances in which a core dump file is not produced:
* The process does not have permission to write the core file. (By default the core file is called 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 non-writable, 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).
* 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.
* The file system 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 file system.
* The directory in which the core dump file is to be created does not exist.
* The RLIMIT_CORE (core file size) or RLIMIT_FSIZE (file size) resource limits for the process are set to zero; see getr-
limit(2) and the documentation of the shell's ulimit command (limit in csh(1)).
* The binary being executed by the process does not have read permission enabled.
* 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 prctl(2) PR_SET_DUMPABLE operation, and the description of
the /proc/sys/fs/suid_dumpable file in proc(5).)
Naming of core dump files
By default, a core dump file is named core, but the /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:
%% a single % character
%p PID of dumped process
%u (numeric) real UID of dumped process
%g (numeric) real GID of dumped process
%s number of signal causing dump
%t time of dump, expressed as seconds since the Epoch (00:00h, 1 Jan 1970, UTC)
%h hostname (same as nodename returned by uname(2))
%e executable filename (without path prefix)
%c core file size soft resource limit of crashing process (since Linux 2.6.24)
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 '/' 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 compatibil-
ity, if /proc/sys/kernel/core_pattern does not include "%p" and /proc/sys/kernel/core_uses_pid (see below) is non-zero, 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
/proc/sys/kernel/core_uses_pid file contains the value 0, then a core dump file is simply named core. If this file contains a
non-zero value, then the core dump file includes the process ID in a name of the form core.PID.
Piping core dumps to a program
Since kernel 2.6.19, Linux supports an alternate syntax for the /proc/sys/kernel/core_pattern file. If the first character of
this file is a pipe symbol (|), 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:
* The program must be specified using an absolute pathname (or a pathname relative to the root directory, /), and must immedi-
ately follow the '|' character.
* The process created to run the program runs as user and group root.
* Command-line arguments can be supplied to the program (since kernel 2.6.24), delimited by white space (up to a total line
length of 128 bytes).
* 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 %p in an argument.
Controlling which mappings are written to the core dump
Since kernel 2.6.23, the Linux-specific /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 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:
bit 0 Dump anonymous private mappings.
bit 1 Dump anonymous shared mappings.
bit 2 Dump file-backed private mappings.
bit 3 Dump file-backed shared mappings.
The default value of coredump_filter is 0x3; this reflects traditional Linux behavior and means that only anonymous memory seg-
ments are dumped.
Memory-mapped I/O pages such as frame buffer are never dumped, and virtual DSO pages are always dumped, regardless of the core-
dump_filter value.
A child process created via fork(2) inherits its parents coredump_filter value; the coredump_filter value is preserved across an
execve(2).
It can be useful to set coredump_filter in the parent shell before running a program, for example:
$ echo 0x7 > /proc/self/coredump_filter
$ ./some_program
This file is only provided if the kernel was built with the CONFIG_ELF_CORE configuration option.
NOTES
The gdb(1) gcore command can be used to obtain a core dump of a running process.
If a multithreaded process (or, more precisely, a process that shares its memory with another process by being created with the
CLONE_VM flag of 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 /proc/sys/kernel/core_pattern. (This is primarily useful
when employing the LinuxThreads implementation, where each thread of a process has a different PID.)
EXAMPLE
The program below can be used to demonstrate the use of the pipe syntax in the /proc/sys/kernel/core_pattern file. The follow-
ing shell session demonstrates the use of this program (compiled to create an executable named core_pattern_pipe_test):
$ cc -o core_pattern_pipe_test core_pattern_pipe_test.c
$ su
Password:
# echo '|$PWD/core_pattern_pipe_test %p UID=%u GID=%g sig=%s' > \
/proc/sys/kernel/core_pattern
# exit
$ sleep 100
^\ # type control-backslash
Quit (core dumped)
$ 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
Program source
/* 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);
exit(EXIT_SUCCESS);
}
core - core dump file
DESCRIPTION
The default action of certain signals is to cause a process to terminate and produce a 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., 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
signal(7).
A process can set its soft 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 getrlimit(2) for details.
There are various circumstances in which a core dump file is not produced:
* The process does not have permission to write the core file. (By default the core file is called 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 non-writable, 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).
* 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.
* The file system 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 file system.
* The directory in which the core dump file is to be created does not exist.
* The RLIMIT_CORE (core file size) or RLIMIT_FSIZE (file size) resource limits for the process are set to zero; see getr-
limit(2) and the documentation of the shell's ulimit command (limit in csh(1)).
* The binary being executed by the process does not have read permission enabled.
* 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 prctl(2) PR_SET_DUMPABLE operation, and the description of
the /proc/sys/fs/suid_dumpable file in proc(5).)
Naming of core dump files
By default, a core dump file is named core, but the /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:
%% a single % character
%p PID of dumped process
%u (numeric) real UID of dumped process
%g (numeric) real GID of dumped process
%s number of signal causing dump
%t time of dump, expressed as seconds since the Epoch (00:00h, 1 Jan 1970, UTC)
%h hostname (same as nodename returned by uname(2))
%e executable filename (without path prefix)
%c core file size soft resource limit of crashing process (since Linux 2.6.24)
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 '/' 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 compatibil-
ity, if /proc/sys/kernel/core_pattern does not include "%p" and /proc/sys/kernel/core_uses_pid (see below) is non-zero, 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
/proc/sys/kernel/core_uses_pid file contains the value 0, then a core dump file is simply named core. If this file contains a
non-zero value, then the core dump file includes the process ID in a name of the form core.PID.
Piping core dumps to a program
Since kernel 2.6.19, Linux supports an alternate syntax for the /proc/sys/kernel/core_pattern file. If the first character of
this file is a pipe symbol (|), 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:
* The program must be specified using an absolute pathname (or a pathname relative to the root directory, /), and must immedi-
ately follow the '|' character.
* The process created to run the program runs as user and group root.
* Command-line arguments can be supplied to the program (since kernel 2.6.24), delimited by white space (up to a total line
length of 128 bytes).
* 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 %p in an argument.
Controlling which mappings are written to the core dump
Since kernel 2.6.23, the Linux-specific /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 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:
bit 0 Dump anonymous private mappings.
bit 1 Dump anonymous shared mappings.
bit 2 Dump file-backed private mappings.
bit 3 Dump file-backed shared mappings.
The default value of coredump_filter is 0x3; this reflects traditional Linux behavior and means that only anonymous memory seg-
ments are dumped.
Memory-mapped I/O pages such as frame buffer are never dumped, and virtual DSO pages are always dumped, regardless of the core-
dump_filter value.
A child process created via fork(2) inherits its parents coredump_filter value; the coredump_filter value is preserved across an
execve(2).
It can be useful to set coredump_filter in the parent shell before running a program, for example:
$ echo 0x7 > /proc/self/coredump_filter
$ ./some_program
This file is only provided if the kernel was built with the CONFIG_ELF_CORE configuration option.
NOTES
The gdb(1) gcore command can be used to obtain a core dump of a running process.
If a multithreaded process (or, more precisely, a process that shares its memory with another process by being created with the
CLONE_VM flag of 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 /proc/sys/kernel/core_pattern. (This is primarily useful
when employing the LinuxThreads implementation, where each thread of a process has a different PID.)
EXAMPLE
The program below can be used to demonstrate the use of the pipe syntax in the /proc/sys/kernel/core_pattern file. The follow-
ing shell session demonstrates the use of this program (compiled to create an executable named core_pattern_pipe_test):
$ cc -o core_pattern_pipe_test core_pattern_pipe_test.c
$ su
Password:
# echo '|$PWD/core_pattern_pipe_test %p UID=%u GID=%g sig=%s' > \
/proc/sys/kernel/core_pattern
# exit
$ sleep 100
^\ # type control-backslash
Quit (core dumped)
$ 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
Program source
/* 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);
exit(EXIT_SUCCESS);
}
영구적으로 세팅하기 위해서는 다음과 같이 수정하시면 됩니다.
vi /etc/sysctl.conf
kernel.core_pattern = [ path ]/core/%e-%t-%p.core
수정후,
sysctl -p
패턴 확인하는 방법은
testuser@linux:/etc> cat /proc/sys/kernel/core_pattern
/home/testuser/core/%e-%t-%p.core
/home/testuser/core/%e-%t-%p.core