Arch Linux uses systemd, and the core dump files will be stored in /var/lib/systemd/coredump directory by default.
Let’s look at the following simple program:
int main(void) {
int *p = 0;
*p = 1;
}
Compile and run it:
$ gcc -g -o test test.c
$ ./test
Segmentation fault (core dumped)
Definitely, the program crashes! Check the core dump files:
$ coredumpctl list
TIME PID UID GID SIG COREFILE EXE
......
Mon 2017-01-09 16:13:44 SGT 7307 1014 1014 11 present /home/xiaonan/test
$ ls -alt /var/lib/systemd/coredump/core.test*
-rw-r-----+ 1 root root 22821 Jan 9 16:13 /var/lib/systemd/coredump/core.test.1014.183b4c57ccad464abd2eba2c104a47a8.7307.1483949624000000000000.lz4
According to the file name and time, we can find the program’s corresponding core dump binary. To debug it, we can use “coredumpctl gdb PID” command:
$ coredumpctl gdb 7307
PID: 7307 (test)
UID: 1014 (xiaonan)
GID: 1014 (xiaonan)
Signal: 11 (SEGV)
Timestamp: Mon 2017-01-09 16:13:44 SGT (6min ago)
Command Line: ./test
Executable: /home/xiaonan/test
Control Group: /user.slice/user-1014.slice/session-c4.scope
Unit: session-c4.scope
Slice: user-1014.slice
Session: c4
Owner UID: 1014 (xiaonan)
Boot ID: 183b4c57ccad464abd2eba2c104a47a8
Machine ID: 25671e5feadb4ae4bbe2c9ee6de97d66
Hostname: supermicro-sys-1028gq-trt
Storage: /var/lib/systemd/coredump/core.test.1014.183b4c57ccad464abd2eba2c104a47a8.7307.1483949624000000000000.lz4
Message: Process 7307 (test) of user 1014 dumped core.
Stack trace of thread 7307:
#0 0x00000000004004b6 main (test)
#1 0x00007f67ba722291 __libc_start_main (libc.so.6)
#2 0x00000000004003da _start (test)
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Reading symbols from /home/xiaonan/test...done.
[New LWP 7307]
Core was generated by `./test'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00000000004004b6 in main () at test.c:3
3 *p = 1;
(gdb) bt
#0 0x00000000004004b6 in main () at test.c:3
BTW, if you omit PID, “coredumpctl gdb” will launch the newest core dump file.
Attention should be paid. The core dump size is limited to 2GiB, so if it is too large, it will be truncated, and generate the warning like this (Please refer this bug):
......
BFD: Warning: /var/tmp/coredump-ZrhAM4 is truncated: expected core file size >= 2591764480, found: 2147483648.
......
References:
GDB and trouble with core dumps;
Core dump.