Enabling core dumps on crashes

Add this line to /etc/sysctl.conf:

kernel.core_pattern = /tmp/%t.%p.core

To enable it without rebooting, run:

sysctl -w 'kernel.core_pattern = /tmp/%t.%p.core'

If Prosody has been given the capability to bind low ports then this counts as suid, which in turn disables core dumps. This can be bypassed with:

fs.suid_dumpable = 1

In your prosody.cfg.lua add:

require"util.pposix".setrlimit("CORE", "unlimited", "unlimited")

Getting a core dump from a running Prosody

Without killing it.

prosodyctl status
# should print eg Prosody is running with PID 1234
gcore -o prosody 1234

This should produce a file prosody.1234.

Getting a backtrace

Open the core dump using gdb -c prosody.1234 /usr/bin/lua5.1, then you can get a backtrace using bt or more vebosely with bt full.