How to generate a core dump in Linux on a segmenta

Question

I have a process in Linux that's getting a segmentation fault. How can I tell it to generate a core dump when it fails?

Answer 1

For Ubuntu 14.04

1. Check core dump enabled:

   ulimit -a
   

2. One of the lines should be :

   core file size          (blocks, -c) unlimited
   

3. If not :

   gedit ~/.bashrc and add ulimit -c unlimited to end of file and save, re-run terminal.

4. Build your application with debug information :

   In Makefile -O0 -g

5. Run application that create core dump (core dump file with name ‘core’ should be created near application_name file):

   ./application_name
   

6. Run under gdb:

   gdb application_name core
   

Answer 2

To check where the core dumps are generated, run:

sysctl kernel.core_pattern

or:

cat /proc/sys/kernel/core_pattern

where %e is the process name and %t the system time. You can change it in /etc/sysctl.conf and reloading by sysctl -p.

If the core files are not generated (test it by: sleep 10 & and killall -SIGSEGV sleep), check the limits by: ulimit -a.

If your core file size is limited, run:

ulimit -c unlimited

to make it unlimited.

Then test again, if the core dumping is successful, you will see “(core dumped)” after the segmentation fault indication as below:

Segmentation fault: 11 (core dumped)

See also: core dumped - but core file is not in current directory?

---

Ubuntu

In Ubuntu the core dumps are handled by Apport and can be located in /var/crash/. However, it is disabled by default in stable releases.

For more details, please check: Where do I find the core dump in Ubuntu?.

macOS

For macOS, see: How to generate core dumps in Mac OS X?

Answer 3

As explained above the real question being asked here is how to enable core dumps on a system where they are not enabled. That question is answered here.

If you've come here hoping to learn how to generate a core dump for a hung process, the answer is

gcore <pid>

if gcore is not available on your system then

kill -ABRT <pid>

Don't use kill -SEGV as that will often invoke a signal handler making it harder to diagnose the stuck process

Answer 4

Ubuntu 19.04

All other answers themselves didn't help me. But the following sum up did the job

Create ~/.config/apport/settings with the following content:

[main]
unpackaged=true

(This tells apport to also write core dumps for custom apps)

check: ulimit -c. If it outputs 0, fix it with

ulimit -c unlimited

Just for in case restart apport:

sudo systemctl restart apport

Crash files are now written in /var/crash/. But you cannot use them with gdb. To use them with gdb, use

apport-unpack <location_of_report> <target_directory>

Further information:

• Some answers suggest changing core_pattern. Be aware, that that file might get overwritten by the apport service on restarting.
• Simply stopping apport did not do the job
• The ulimit -c value might get changed automatically while you're trying other answers of the web. Be sure to check it regularly during setting up your core dump creation.

References:

• https://stackoverflow.com/a/47481884/6702598

Answer 5

Better to turn on core dump programmatically using system call setrlimit.

example:

#include <sys/resource.h>

bool enable_core_dump(){    
    struct rlimit corelim;

    corelim.rlim_cur = RLIM_INFINITY;
    corelim.rlim_max = RLIM_INFINITY;

    return (0 == setrlimit(RLIMIT_CORE, &corelim));
}

Answer 6

By default you will get a core file. Check to see that the current directory of the process is writable, or no core file will be created.