Analyzing Coredumps

This article is about analyzing coredumps in postmarketOS. It's a stub, the part with analyzing doesn't seem to return an useful stack in most cases, expanding this and removing this sentence is most welcome.

Enabling Coredumps

Unlike your typical systemd based distribution, we don't use coredumpctl and coredumps are not enabled by default, so you need to do the following steps first.

1. Write to /etc/security/limits.conf:

# <domain> <type> <item> <value>
* soft core unlimited
* hard core unlimited

2. Set a pattern for writing the core dumps, e.g.:

$ echo '/tmp/core.%e.%p' | sudo tee /proc/sys/kernel/core_pattern

If you use a different directory, make sure all users can write to it by using chmod a+w.

3. Set ulimit before running the application that you want to debug. It is valid for the current shell session. If you want everything that runs in tinydm to create coredumps, put this in ~/.profile:

ulimit -c unlimited

Verifying that it works

If you are unsure whether this works, e.g. because the app you expect to crash doesn't create a coredump for some reason, build a simple C program that crashes:

$ echo '#include <stdlib.h>\nint main() { abort(); return 0; }' > /tmp/crash.c
$ gcc -o /tmp/crash /tmp/crash.c
$ /tmp/crash 
[1]    28898 abort      /tmp/crash