現象
通過gdb開啟core，但看不到core的內容，資訊如下：

$ gdb XXX core.XXX
GNU gdb (GDB) Red Hat Enterprise Linux ( 7.0.1-32.el5)
Copyright (C) 2009 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".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/XXX/XXX...done.
BFD: Warning: /home/XXX/core.XXX is truncated: expected core file
 
 size >= 747175936, found: 1236992.

warning: core file may not match specified executable file.
Cannot access memory at address 0x344201cc88

調查
ulimit -a的結果如下：

core file size          (blocks, -c) 1000
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f
 
) unlimited
pending signals                 (-i) 40960
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65000
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 536870912
real-time priority              (-r) 0
stack size              (kbytes, -s) 1024000
cpu time               (seconds, -t) unlimited
max user processes              (-u) 40960
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

經別人指點，說是“core file size”的值太小了。

修改core file size的方法
1 使用root使用者登入，在/etc/security/limits.conf檔案中，添加了“* hard core unlimited”行，新增後此檔案的內容大致如下：

# /etc/security/limits.conf
#
# Each line describes a limit for a user in the form:
#
# <domain> <type> <item> <value>
#
* - msgqueue 536870912
* soft nofile 65000
* hard nofile 65000
* soft core   unlimited
* hard core   unlimited

2 修改這個檔案後，退出root使用者
3 退出自己的賬戶的全部登入的終端，然後關閉telnet工具，重新使用自己的賬戶登入系統，鍵入下面的命令，都會返回unlimited

$ ulimit -S -c
unlimited
$ ulimit -H -c
unlimited

此時core檔案就不會被截斷了。