Plurrrr

A signal is an event that Linux systems generate in response to some condition. Signals can be sent by the kernel to a process, by a process to another process, or a process to itself. Upon receipt of a signal, a process may take action.

Signals are a core part of Unix-like operating environments and have existed since more or less the dawn of time. They are the plumbing for many of the core components of the operating system—core dumping, process life cycle management, etc.—and in general, they've held up pretty well in the fifty or so years that we have been using them. As such, when somebody suggests that using them for interprocess communication (IPC) is potentially dangerous, one might think these are the ramblings of someone desperate to invent the wheel. However, this article is intended to demonstrate cases where signals have been the cause of production issues and offer some potential mitigations and alternatives.

One of the most useful, but often misunderstood and misconfigured, features of NGINX is rate limiting. It allows you to limit the amount of HTTP requests a user can make in a given period of time. A request can be as simple as a GET request for the homepage of a website or a POST request on a log‑in form.

Rate limiting can be used for security purposes, for example to slow down brute‑force password‑guessing attacks. It can help protect against DDoS attacks by limiting the incoming request rate to a value typical for real users, and (with logging) identify the targeted URLs. More generally, it is used to protect upstream application servers from being overwhelmed by too many user requests at the same time.

In this blog we will cover the basics of rate limiting with NGINX as well as more advanced configurations. Rate limiting works the same way in NGINX Plus.

The FreeBSD operating system contains innumerable powerful features. One of these features is bhyve, its native type 2 (OS-level) hypervisor, which can host virtual machines running multiple different OSes, including Linux.

This post will walk you through creating a Linux virtual machine on FreeBSD using the CBSD tool, which greatly simplifies creating and managing bhyve VMs.