Haoyuan Ge harryge00

Kafka Topics

List existing topics

bin/kafka-topics.sh --zookeeper localhost:2181 --list

Describe a topic

bin/kafka-topics.sh --zookeeper localhost:2181 --describe --topic mytopic

Purge a topic

bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic mytopic --config retention.ms=1000

... wait a minute ...

Understanding the Memory Layout of Linux Executables

Required tools for playing around with memory:

hexdump
objdump
readelf
xxd
gcore

How to install redis-cli and psql client on your machine with Docker

Preparing docker images

We will use minimalistic Linux distribution called Alpine (5MB)

Dockerfile of redis-cli

FROM alpine:latest
RUN apk --update add redis

Some examples of SNAT, DNAT with iptables with comments

mainly used in start-up script

How to test 'safely'

When we play with iptables aka firewall we might end up in situation, where we execute rule, which has unforseen impact - lock yourself out. Recovering from this situation is necessity.

How to:

Enable reboot via SMS.

Test all commands in shell first before putting them into Start-up script. This way the command will be wiped out, when unit is rebooted.

masquarade all outgoing packets to be WLAN0 IP

Client-side SSL

For excessively paranoid client authentication.

Updated Apr 5 2019:

because this is a gist from 2011 that people stumble into and maybe you should AES instead of 3DES in the year of our lord 2019.

some other notes:

	$ ./bin/spark-shell
	14/04/18 15:23:49 INFO spark.HttpServer: Starting HTTP Server
	14/04/18 15:23:49 INFO server.Server: jetty-7.x.y-SNAPSHOT
	14/04/18 15:23:49 INFO server.AbstractConnector: Started [email protected]:49861
	Welcome to
	____ __
	/ __/__ ___ _____/ /__
	_\ \/ _ \/ _ `/ __/ '_/
	/___/ .__/\_,_/_/ /_/\_\ version 0.9.1
	/_/

	package main

	import "fmt"

	// fibonacci is a function that returns
	// a function that returns an int.
	func fibonacci() func() int {
	f2, f1 := 0, 1
	return func() int {
	f := f2