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Create Root CA (Done once)

Last update: Nov 2025.

Create Root Key

Attention: this is the key used to sign the certificate requests, anyone holding this can sign certificates on your behalf. So keep it in a safe place!

openssl ecparam -genkey -name secp384r1 | openssl ec -aes256 -out rootCA.key

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ELF Format Cheatsheet

Introduction

Executable and Linkable Format (ELF), is the default binary format on Linux-based systems.

Compilation

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Seccomp BPF filter example

Use bpf programs as filters for seccomp, the one in the example will block all the write syscalls after it's loaded.

Usage

Compile it with just

gcc main.c

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Install i3

dnf install i3

Add exec i3 to xinitrc

echo "exec i3" > ~/.xinitrc

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InfluxDB and Chronograf in Kubernetes

1. Create the namespace

kubectl create ns monitoring

2. Deploy influxdb

kubectl apply -f influxdb.yml

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Compile with gcc
gcc -nostdlib main.c 

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The eBPF verifier

Important: This article was written by Github Copilot, while it's not entirely accurate, it's quite good to see what it ended up with.

The bpf verifier is a tool that can be used to check the correctness of eBPF programs. It is implemented in C and is used by the kernel. When the kernel is built with CONFIG_BPF_JIT, it does further optimization on the BPF programs.

To write a valid eBPF program you need to follow a few rules:

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#include <linux/bpf.h>
#include <linux/in.h>
#include <linux/if_ether.h>
#include <linux/ip.h>

#define SEC(NAME) __attribute__((section(NAME), used))

SEC("dropper_main")
int dropper(struct xdp_md *ctx) {
  int ipsize = 0;

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Flux as a Library Example

Flux is a lightweight scripting language for querying databases (like InfluxDB) and working with data. It's part of InfluxDB 1.7 and 2.0, but can be run independently of those.

This gist contains a main.go file that shows how flux can be used as a library in your programs.

Components

The main components you need are:

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[[constraint]]
  name = "k8s.io/api"
  version = "kubernetes-1.11.0"

[[constraint]]
  name = "k8s.io/apimachinery"
  version = "kubernetes-1.11.0"

[[constraint]]
  name = "k8s.io/client-go"