什么是core dump？
Coredump叫做核心轉儲，它是進程運行時在突然崩潰的那一刻的一個內存快照。操作系統在程序發生異常而異常在進程內部又沒有被捕獲的情況下，會把進程此刻內存、寄存器狀態、運行堆棧等信息轉儲保存在一個二進制文件里。
設置core dump文件大小，默認0，即不會生成core文件
ulimit -c unlimited
設置core dump文件的位置文件名格式，%e和%p會被替換成程序文件名以及進程ID。缺省情況下，內核在coredump時所產生的core文件放在與該程序相同的目錄中，並且文件名固定為core。
echo “data/coredump/core.%e.%p”> /proc/sys/kernel/core_pattern
core文件調試
1:
編譯加-g參數
2:
gdb program core
手動生成core文件
程序卡死的時候，有時需要把卡死狀態保持起來，生成core文件，然后慢慢分析。
gcore
usage: gcore [-o filename] pid
gdb的generate-core-file命令
[root@htdev ~]# gdb attach 19388
GNU gdb Fedora (6.8-37.el5)
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later http://gnu.org/licenses/gpl.html
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu"...
attach: No such file or directory.
Attaching to process 19388
Reading symbols from /usr/local/bin/node...done.
Reading symbols from /lib64/librt.so.1...done.
Loaded symbols for /lib64/librt.so.1
Reading symbols from /lib64/libdl.so.2...done.
Loaded symbols for /lib64/libdl.so.2
Reading symbols from /usr/lib64/libstdc++.so.6...done.
Loaded symbols for /usr/lib64/libstdc++.so.6
Reading symbols from /lib64/libm.so.6...done.
Loaded symbols for /lib64/libm.so.6
Reading symbols from /lib64/libgcc_s.so.1...done.
Loaded symbols for /lib64/libgcc_s.so.1
Reading symbols from /lib64/libpthread.so.0...done.
[Thread debugging using libthread_db enabled]
[New Thread 0x2b46ed999890 (LWP 19388)]
[New Thread 0x43e62940 (LWP 19399)]
[New Thread 0x43461940 (LWP 19398)]
[New Thread 0x42a60940 (LWP 19397)]
[New Thread 0x4205f940 (LWP 19396)]
[New Thread 0x41018940 (LWP 19390)]
[New Thread 0x41007940 (LWP 19389)]
Loaded symbols for /lib64/libpthread.so.0
Reading symbols from /lib64/libc.so.6...done.
Loaded symbols for /lib64/libc.so.6
Reading symbols from /lib64/ld-linux-x86-64.so.2...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Reading symbols from /root/eicn/work/web/node_modules/hiredis/build/Release/hiredis.node...done.
Loaded symbols for /root/eicn/work/web/node_modules/hiredis/build/Release/hiredis.node
0x000000364b4d06d9 in syscall () from /lib64/libc.so.6
(gdb) generate-core-file
Saved corefile core.19388
(gdb) detach
Detaching from program: /usr/local/bin/node, process 19388
設置core文件路徑
1.編輯環境配置文件，讓shell啟動時自動設置ulimit
2.更改core文件生成路徑
3.sysctl配置生效
vi /etc/profile
ulimit -c unlimited > /dev/null 2>&1
vi /etc/sysctl.conf
kernel.core_uses_pid = 1
kernel.core_pattern=/tmp/core-%e-%p
sysctl -p /etc/sysctl.conf