wanyaoqi

How to update the Go version

System: Debian/Ubuntu/Fedora. Might work for others as well.

1. Uninstall the exisiting version

As mentioned here, to update a go version you will first need to uninstall the original version.

To uninstall, delete the /usr/local/go directory by:

Recovering deleted files in Ubuntu with ext4 filesystem

Recently, I deleted some files by mistake in a Ubuntu machine with an ext4 fs. These notes document the steps I took to get them back.

Important

this procedure assumes that the partition that contained the deleted files is different from the root partition, as that was the scenario with which I had to deal (deleted files were in my home dir). The procedure needs that the partition that contained the files is unmounted, so if the deleted files were in the root partition, the process would be a bit different (e.g. storing the fs journal in a USB stick, using a live CD/USB to boot and issue the commands, etc.)
if something is not clear, you need more information, etc. check the sources below

With that out the way, let's begin.

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

	Windows批处理(cmd/bat)常用命令小结

	前言
	批处理文件（batch file）包含一系列 DOS命令，通常用于自动执行重复性任务。用户只需双击批处理文件便可执行任务，而无需重复输入相同指令。
	编写批处理文件非常简单，但难点在于确保一切按顺序执行。编写严谨的批处理文件可以极大程度地节省时间，在应对重复性工作时尤其有效。

	在Windows中善用批处理可以简化很多重复工作

	阅读原文 - https://wsgzao.github.io/post/windows-batch/

	#!/bin/bash

	echo "Removing old ovs configuration."
	sudo /etc/init.d/openvswitch-switch stop
	sudo kill `cd /usr/local/var/run/openvswitch && cat ovsdb-server.pid ovs-vswitchd.pid`
	sudo rm -rf /usr/local/var/run/openvswitch
	sudo mkdir -p /usr/local/var/run/openvswitch
	sudo rm -rf /usr/local/etc/openvswitch
	sudo mkdir -p /usr/local/etc/openvswitch
	sudo rm -rf /var/run/openvswitch

	package main

	import (
	"fmt"
	"os"
	"os/exec"
	"syscall"
	)

	func main() {

	import (
	"crypto/md5"
	"encoding/hex"
	)

	func GetMD5Hash(text string) string {
	hasher := md5.New()
	hasher.Write([]byte(text))
	return hex.EncodeToString(hasher.Sum(nil))
	}