Troubleshooting sysctl: cannot stat /proc/sys/kernel/core_name_format: No such file or directory Set core dump file name pattern core_pattern
/etc/sysctl.confcaused error: sysctl: cannot stat /proc/sys/kernel/core_name_format: No such file or directory
What is core dump
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) to inspect the state of the program at the time that it terminated.
In some Linux, the default core dump file name is
core. If there are multiple core dump happen, the later
core will override the previous one. To keep the all the core dump files for easier core dumps debugging, different core dump should have different name.
core dump is disabled by default, to enable core dump, use
$ ulimit -c unlimited
Then you will see:
$ ulimit -c unlimited $ ulimit -a | grep core core file size (blocks, -c) unlimited
There is suggestion to use
kernel.core_name_format control coredump file name, but got following error:
$ sudo sysctl -w kernel.core_name_format="core.%e.%p.%s.%t" sysctl: cannot stat /proc/sys/kernel/core_name_format: No such file or directory
kernel.core_name_format is not exist in kernel parameters,
the correct one is
$ sudo sysctl -w kernel.core_pattern="core.%e.%p.%s.%t" kernel.core_pattern = core.%e.%p.%s.%t
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
%ccore file size soft resource limit of crashing process (since Linux 2.6.24)
%ddump mode—same as value returned by
PR_GET_DUMPABLE(since Linux 3.7)
%eexecutable filename (without path prefix)
%Epathname of executable, with slashes ('/') replaced by exclamation marks ('!') (since Linux 3.0).
%g(numeric) real GID of dumped process
%hhostname (same as nodename returned by uname(2))
%iTID of thread that triggered core dump, as seen in the PID namespace in which the thread resides (since Linux 3.18)
%ITID of thread that triggered core dump, as seen in the initial PID namespace (since Linux 3.18)
%pPID of dumped process, as seen in the PID namespace in which the process resides
%PPID of dumped process, as seen in the initial PID namespace (since Linux 3.12)
%snumber of signal causing dump
%ttime of dump, expressed as seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC)
%u(numeric) real UID of dumped process
Debugging core file
gdb command used for a core dump file debugging is
backtrace) to show the crash stack.
f <n> (or
frame <n>) to switch to function call,
info locals and
info args also helpfule.
gdb session for a core dump debugging:
$ gdb a.out core ... ... Type "apropos word" to search for commands related to "word"... Reading symbols from a.out...done. [New LWP 17239] [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1". btCore was generated by `./a.out'. Program terminated with signal SIGABRT, Aborted. #0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50 50 ../sysdeps/unix/sysv/linux/raise.c: No such file or directory. (gdb) bt #0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50 #1 0x76e06230 in __GI_abort () at abort.c:79 #2 0x00015308 in bar (x=0x1eb6fa8) at foo.c:196 #3 0x00014834 in foo (x=0x1eb6fa8, y=0x1ba9c90) at foo.c:310 #4 0x00014660 in main (argc=1, argv=0x7ea78684) at foo.c:272 (gdb) f 3 #3 0x00014834 in foo (x=0x1eb6fa8, y=0x1ba9c90) at proxyd/proxyd.c:310 310 ret = bar(x); (gdb) info args x = 0x1eb6fa8 y = 0x1ba9c90 (gdb) info locals ret = 32354640 ...
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