What killed my process and why?

Question

My application runs as a background process on Linux. It is currently started at the command line in a Terminal window.

Recently a user was executing the application

Answer 1

A tool like systemtap (or a tracer) can monitor kernel signal-transmission logic and report. e.g., https://sourceware.org/systemtap/examples/process/sigmon.stp

# stap .../sigmon.stp -x 31994 SIGKILL
   SPID     SNAME            RPID  RNAME            SIGNUM SIGNAME
   5609     bash             31994 find             9      SIGKILL

The filtering if block in that script can be adjusted to taste, or eliminated to trace systemwide signal traffic. Causes can be further isolated by collecting backtraces (add a print_backtrace() and/or print_ubacktrace() to the probe, for kernel- and userspace- respectively).