Chuang Zhu chuangzhu

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Basic HTML Meta Tags

<meta name="keywords" content="your, tags"/>
<meta name="description" content="150 words"/>
<meta name="subject" content="your website's subject">
<meta name="copyright"content="company name">
<meta name="language" content="ES">

ffmpeg

Converting Audio into Different Formats / Sample Rates

Minimal example: transcode from MP3 to WMA:
ffmpeg -i input.mp3 output.wma

You can get the list of supported formats with:
ffmpeg -formats

You can get the list of installed codecs with:

IPv6	国家	省份	城市	学校/教育机构
2001:da8:0200::/48	中国	北京	北京	清华大学
2001:da8:0201::/48	中国	北京	北京	北京大学
2001:da8:0202::/48	中国	北京	北京	北京邮电大学
2001:da8:0203::/48	中国	北京	北京	北京航空航天大学
2001:da8:0204::/48	中国	北京	北京	北京理工大学
2001:da8:0205::/48	中国	北京	北京	北京交通大学
2001:da8:0206::/48	中国	北京	北京	北京城市学院
2001:da8:0207::/48	中国	北京	北京	北京师范大学
2001:da8:0208::/48	中国	北京	北京	北京科技大学

Installing NixOS on the RockPi4 (B)

The general plan is to build an sd-image-aarch64 from nixpkgs/nixos/modules/installer/cd-dvd/sd-image-aarch64.nix flash it to the eMMC and have the system come up, similar to how this “just works” for raspberry-pis.

The RockPi 4 is a RockChip RK3399 based board, build by radxa with the same formfactor as a rasperry Pi. One noticable difference is that the Rock Pi’s cpu is at the bottom to better allow for the

	# Hello, and welcome to makefile basics.
	#
	# You will learn why `make` is so great, and why, despite its "weird" syntax,
	# it is actually a highly expressive, efficient, and powerful way to build
	# programs.
	#
	# Once you're done here, go to
	# http://www.gnu.org/software/make/manual/make.html
	# to learn SOOOO much more.

	<!DOCTYPE html>
	<html>
	<head>
	<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.css" />
	<script src="http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.js"></script>
	<style>
	body { padding: 0; margin: 0; }
	html, body, #map { height: 100%; }
	</style>
	</head>

	# Source:
	# https://www.cloudflare.com/ips
	# https://support.cloudflare.com/hc/en-us/articles/200169166-How-do-I-whitelist-CloudFlare-s-IP-addresses-in-iptables-

	for i in `curl https://www.cloudflare.com/ips-v4`; do iptables -I INPUT -p tcp -m multiport --dports http,https -s $i -j ACCEPT; done
	for i in `curl https://www.cloudflare.com/ips-v6`; do ip6tables -I INPUT -p tcp -m multiport --dports http,https -s $i -j ACCEPT; done

	# Avoid racking up billing/attacks
	# WARNING: If you get attacked and CloudFlare drops you, your site(s) will be unreachable.
	iptables -A INPUT -p tcp -m multiport --dports http,https -j DROP

	# Should work on all Debian based distros with systemd; tested on Ubuntu 16.04+.
	# This will by default install all plugins; you can customize this behavior on line 6. Selecting too many plugins can cause issues when downloading.
	# Run as root (or sudo before every line) please. Note this is not designed to be run automatically; I recommend executing this line by line.

	apt install curl
	curl https://getcaddy.com \| bash -s personal dns,docker,dyndns,hook.service,http.authz,http.awses,http.awslambda,http.cache,http.cgi,http.cors,http.datadog,http.expires,http.filemanager,http.filter,http.forwardproxy,http.geoip,http.git,http.gopkg,http.grpc,http.hugo,http.ipfilter,http.jekyll,http.jwt,http.locale,http.login,http.mailout,http.minify,http.nobots,http.prometheus,http.proxyprotocol,http.ratelimit,http.realip,http.reauth,http.restic,http.upload,http.webdav,net,tls.dns.auroradns,tls.dns.azure,tls.dns.cloudflare,tls.dns.cloudxns,tls.dns.digitalocean,tls.dns.dnsimple,tls.dns.dnsmadeeasy,tls.dns.dnspod,tls.dns.dyn,tls.

	# Copyright (c) 2017 Stanislav Bobokalo & Alexey Borontov

	# Permission is hereby granted, free of charge, to any person obtaining a copy
	# of this software and associated documentation files (the "Software"), to deal
	# in the Software without restriction, including without limitation the rights
	# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	# copies of the Software, and to permit persons to whom the Software is
	# furnished to do so, subject to the following conditions:

	# The above copyright notice and this permission notice shall be included in all

	# Edit this configuration file to define what should be installed on
	# your system. Help is available in the configuration.nix(5) man page
	# and in the NixOS manual (accessible by running ‘nixos-help’).

	{ config, pkgs, ... }:

	let
	wallpaper = builtins.fetchurl {
	url = "https://wallpaperplay.com/walls/full/5/3/0/10478.jpg";
	sha256 = "0b73fjimxw0dd58w8wvmlyqld01zdpczz5ih1bl7c4s5jh775x7q";