The core dump file in Arch Linux

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

......
BFD: Warning: /var/tmp/coredump-ZrhAM4 is truncated: expected core file size >= 2591764480, found: 2147483648.
......

References:
GDB and trouble with core dumps;
Core dump.