layout: post

title: Where are my core dump files?

tags:

- linux

- ubuntu

- debug

published: true

One day, on a Ubuntu 22.04 machine, I had to debug my application which segfaults with messages like: `corrupted double-linked list` or `free(): corrupted unsorted chunks`.

I could see an error message:

but could not find the corresponding core dump file anywhere.

Where is it?

After some googling, I could find some articles saying that core dumps are handled by Apport in Ubuntu, but they are not enabled in stable releases.

There were a few solutions for this, and I chose to install `systemd-coredump`:

{% highlight bash %}

$ sudo apt-get install systemd-coredump

{% endhighlight %}

After installing systemd-coredump, and running my faulty application, it finally generated a core dump file.

I could find it in `/var/lib/systemd/coredump/`:

{% highlight bash %}

$ ls /var/lib/systemd/coredump/

core.my_faulty_application.9999.abcdefghijklmnopqrstuvwxyz012345.123456.0000000000000000.zst

{% endhighlight %}

List the dumped files,

{% highlight bash %}

$ coredumpctl list

TIME PID UID GID SIG COREFILE EXE SIZE

Thu 2022-11-10 15:59:05 KST 123456 9999 9999 SIGABRT present /path/to/my_faulty_application 2.0M

{% endhighlight %}

dump desired one into the current directory,

{% highlight bash %}

$ coredumpctl dump 123456 --output ./coredump

{% endhighlight %}

and debug it with:

{% highlight bash %}

$ gdb /path/to/my_faulty_application ./coredump

{% endhighlight %}

or debug directly with coredumpctl:

{% highlight bash %}

$ coredumpctl debug 123456

{% endhighlight %}

Some linux distributions don't enable core dumps due to security or storage issues.

When needed, they can be enabled and help debugging things.