* [grml](https://grml.org) – bootable Debian Live CD with powerful CLI tools.
* [mitmproxy](http://mitmproxy.org/) - A Python tool used for intercepting, viewing and modifying network traffic. Invaluable in troubleshooting certain problems.
* [mtr](https://www.bitwizard.nl/mtr/) - Network utility that combines traceroute and ping.
* [perf-tools](https://github.com/brendangregg/perf-tools) - Performance analysis tools based on Linux perf_events (aka perf) and ftrace.
* [Sysdig](http://www.sysdig.org/) - Capture system state and activity from a running Linux instance, then save, filter and analyze.