docs: Explain SIGUSR1 usage in dev guide
Add details to the developer guide of how to obtain a backtrace by
sending a `SIGUSR1` signal to the component.
Fixes
@@ -277,6 +277,18 @@ To perform analysis on Kata logs, use the
[`kata-log-parser`](https://github.com/kata-containers/tests/tree/master/cmd/log-parser)
tool, which can convert the logs into formats (e.g. JSON, TOML, XML, and YAML).
+To obtain a full backtrace for the agent, proxy, runtime, or shim send the
+`SIGUSR1` signal to the process ID of the component. The component will send a
+backtrace to the system log on the host system and continue to run without
+interruption.
+
+For example, to obtain a backtrace for `kata-proxy`:
+
+```
+$ sudo kill -USR1 $kata_proxy_pid
+$ sudo journalctl -t kata-proxy
+```
+
# Appendices
## Checking Docker default runtime
