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    How to create and debug a core dump file

    RyanBy Updated:2 Mins Read

    Debugging programs is not fun or easy but knowing how to create and analyze a core file dump from a dying program makes your life a bit easier.

    First off check the system core dump size limit.
    $ ulimit -c
    0

    Set the maximum size of core files created to unlimited. This must be done each time you start a new login session as it will only change this limit for the current shell.
    $ ulimit -c unlimited

    $ ulimit -c
    unlimited

    Here is the source code for a simple C program that will produce a segfault and a coredump.
    vim coredump.c

    #include <sys/types.h>
    #include <signal.h>
    main()
    {
    kill(getpid(), SIGSEGV);
    }

    Build the program.
    $ make coredump
    cc coredump.c -o coredump

    Now you can run it.
    $ ./coredump
    Segmentation fault (core dumped)

    The core file should now exist in the execution directory.
    $ ls core.*
    core.12345

    Use gdb to look at the core file. This show you the stack trace for each thread in the program. This must be done on the same system since a different system may have different libraries and the results might not be correct.
    $ gdb coredump core.12345
    Reading symbols from /lib64/libc.so.6...(no debugging symbols found)...done.
    Loaded symbols for /lib64/libc.so.6
    Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging symbols found)...done.
    Loaded symbols for /lib64/ld-linux-x86-64.so.2
    Core was generated by `./coredump'.
    Program terminated with signal 11, Segmentation fault.
    #0 0x00000031ba830717 in kill () from /lib64/libc.so.6

    (gdb) thread apply all bt
    Thread 1 (Thread 27701):
    #0 0x00000031ba830717 in kill () from /lib64/libc.so.6
    #1 0x00000000004004f2 in main ()
    (gdb) q

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