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I have a C++ program that does what it is supposed to do, but there must be some problem with pointer, since it crashes at the end and creates a core dump. My problem is that I cannot find the core file, so I cannot debug it.
I have tried
ulimit -c unlimited
ulimit -a
and now the dimension of the file is set to unlimited, but still I cannot find the core. I have tried in every folder written here but still it seems that no core file is created.
Where can I find it?
In Ubuntu the core dumps are handled by Apport and can be located in /var/crash/. But it is disabled by default in stable releases.
To enable Apport, run: sudo systemctl enable apport.service or sudo service apport start.
To disable, run: sudo systemctl disable apport.service or sudo service apport stop in order to back to regular core dumping method. See: How do I enable or disable Apport?.
To disable permanently, edit /etc/apport/crashdb.conf file and comment the following line:
'problem_types': ['Bug', 'Package'],
by adding a hash symbol (#) in the beginning of the line.
To disable crash reporting (back to normal), remove the hash symbol (the same as it was).
You can also check core_pattern, how core dumps are handled by the kernel:
$ cat /proc/sys/kernel/core_pattern
|/usr/share/apport/apport %p %s %c
So even core files are disabled by ulimit, apport will still capture the crash.
See also:
sudo service apport start under Ubuntu 20.04, but no crash dumps appeared in /var/crash.
service apport stop and then the core files appeared in the current directory.
All the above did not worked for me...
I looked at /var/log/apport.log:
cat /var/log/apport.log
and I saw the file name:
ERROR: apport (pid 3426) Mon Nov 8 14:34:07 2021: writing core dump to core._home_guest_a_out.1000.4 ...
and then I search throughout all the system
sudo find . -name "core._home_guest_a_out.1000.4..."
I found the core dump in /var/lib/apport/coredump/
For those googlin': ( in my case -- Ubuntu 16.04 and 18.04 and a custom app ) /var/crash was still empty, so a quick way to handle core creation ( provided that you are e.g. using a relevant ulimit builtin setting ) was
sudo sysctl -w kernel.core_pattern=core.%u.%p.%t # to enable core generation
and
systemctl restart apport # to restore default apport settings
# which, by the way, were "|/usr/share/apport/apport %p %s %c %d %P" (without quotes)
sudo sysctl -w kernel.core_pattern=/tmp/core-%e.%p.%h.%t jvns.ca/blog/2018/04/28/debugging-a-segfault-on-linux
Aug 21, 2020 at 0:09
cwd by default ; have no idea what modern restrictions might apply (e.g. apparmor and the like), and it is probably a good hint for e.g. daemon processes anyway
/var/crash/var/log/apport.log, because modern Ubuntu versions use Apport, which can interfere with core-dumping in non-obvious ways. See stackoverflow.com/a/18368068/1772379 for more info.