Xiaochen Cui XiaochenCui

IP Tables (iptables) Cheat Sheet

IPTables is the Firewall service that is available in a lot of different Linux Distributions. While modifiying it might seem daunting at first, this Cheat Sheet should be able to show you just how easy it is to use and how quickly you can be on your way mucking around with your firewall.

Resources

The following list is a great set of documentation for iptables. I used them to compile this documentation.

How-To Geek: The Beginner’s Guide to iptables, the Linux Firewall: https://www.howtogeek.com/177621/the-beginners-guide-to-iptables-the-linux-firewall/
IPTables Essentials: Common Firewall Rules and COmmands https://www.digitalocean.com/community/tutorials/iptables-essentials-common-firewall-rules-and-commands

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 ...

Configure Git to use a proxy

In Brief

You may need to configure a proxy server if you're having trouble cloning or fetching from a remote repository or getting an error like unable to access '...' Couldn't resolve host '...'.

Consider something like:

Rust/Haskell: Higher-Kinded Types (HKT)

A higher kinded type is a concept that reifies a type constructor as an actual type.

A type constructor can be thought of in these analogies:

like a function in the type universe
as a type with a "hole" in it

	---
	version: '2'
	services:
	zk1:
	image: confluentinc/cp-zookeeper:3.0.1
	ports:
	- "22181:22181"
	environment:
	ZOOKEEPER_SERVER_ID: 1
	ZOOKEEPER_CLIENT_PORT: 22181

	import asyncio
	from django import http
	from django.core.urlresolvers import set_script_prefix
	from django.utils.encoding import force_str
	from django.core.handlers.wsgi import get_script_name
	from django_wsgi.handler import DjangoApplication
	import logging

	import logging
	import sys

	import os, filecmp

	codes = {200:'success',404:'file not found',400:'error',408:'timeout'}

	def compile(file,lang):
	if lang == 'java':
	class_file = file[:-4]+"class"
	elif lang == 'c':
	class_file = file[:-2]
	elif lang=='cpp':

	package main

	import (
	"fmt"
	"net"
	"os"
	"syscall"
	)

	const (

	# On slow systems, checking the cached .zcompdump file to see if it must be
	# regenerated adds a noticable delay to zsh startup. This little hack restricts
	# it to once a day. It should be pasted into your own completion file.
	#
	# The globbing is a little complicated here:
	# - '#q' is an explicit glob qualifier that makes globbing work within zsh's [[ ]] construct.
	# - 'N' makes the glob pattern evaluate to nothing when it doesn't match (rather than throw a globbing error)
	# - '.' matches "regular files"
	# - 'mh+24' matches files (or directories or whatever) that are older than 24 hours.
	autoload -Uz compinit

	rabbitmqctl add_user test test
	rabbitmqctl set_user_tags test administrator
	rabbitmqctl set_permissions -p / test "." "." ".*"