Home » 2015 » December

Springer 免費提供的數學書 (PDF)

Hacker News Daily 上看到有人在 Gist 上把 Springer 提供的數學類 PDF 書籍整理出來 (Direct links to free Springer maths books (pdf versions)),查了一下好像是「Springer launches full book download feature」的一環?:

Springer have made a bunch of maths books available for free, here are the direct links


超小的 Docker Image

Hacker News Daily 上看到「Super small Docker image based on Alpine Linux」這個專案,看了一下是 BusyBox 類的專案,不過套件支援度比起其他 BusyBox 專案多不少。

基於 Alpine Linux 的系統:

Alpine Linux is an independent, non-commercial, general purpose Linux distribution designed for power users who appreciate security, simplicity and resource efficiency.

musl libc 與 BusyBox:

Alpine Linux is built around musl libc and busybox. This makes it smaller and more resource efficient than traditional GNU/Linux distributions. A container requires no more than 8 MB and a minimal installation to disk requires around 130 MB of storage. Not only do you get a fully-fledged Linux environment but a large selection of packages from the repository.

可以拿來玩看看,不過一般狀態下應該還是會拿 UbuntuDebian 的系統來用吧,環境標準多了。(不需要自己花時間找問題)

Android NDK 宣佈向 Clang 靠攏...

Hacker News Daily 上看到 Android NDK 宣佈向 Clang 靠過去的消息:「Changelog for NDK Build 2490520」。

Android NDK 做為效能的加速手段而使用到 C 或是 C++,所以會使用對應的 compiler suite:

The NDK is a toolset that allows you to implement parts of your app using native-code languages such as C and C++. Typically, good use cases for the NDK are CPU-intensive applications such as game engines, signal processing, and physics simulation.


PSA: Everyone should be switching to Clang.


GCC in the NDK is now deprecated.

Amazon EMR 可以在 Private Subnet 裡面執行了...

以前 Amazon EMR 都只能接著 Public IP 跑 (AWS 端會認這個 IP),現在可以丟進 Private Subnet 裡面跑:「New – Launch Amazon EMR Clusters in Private Subnets」。


在今年五月時 Amazon VPC 內有直通 Amazon S3 的介面,不需要再通過 Internet 處理:「Amazon VPC 的 Private Subnet 不需要透過 NAT 去 Amazon S3 抓資料了」。

不過這個架構上還是需要 NAT 連外 (連到 AWS 的系統溝通),不論是傳統的 NAT Instances 或是 NAT Gateways (參考先前的文章「AWS 推出 NAT Gateways」)。



HTTP Status Code 451

前陣子送出的 HTTP Status Code 451 要通過成為標準了:「Why 451?」。

Today, the IESG approved publication of "An HTTP Status Code to Report Legal Obstacles". It'll be an RFC after some work by the RFC Editor and a few more process bits, but effectively you can start using it now.

取自「華氏451度」這部講出版物言論自由的作品 (紙的燃點是華氏 451 度),在 Internet 時代,451 剛好在 HTTP Status Code 4xx 的範圍,被拿來用做「因法令限制而服法提供內容的 Status Code」。


This document specifies a Hypertext Transfer Protocol (HTTP) status code for use when resource access is denied as a consequence of legal demands.

AWS 推出的 aws-shell

AWS 推出的 aws-shell 透過大量的 auto completion 幫助你管理 AWS 的各種資源,可以從官方說明看出是 AWS Command Line Interface (aws-cli) 的延伸:

An integrated shell for working with the AWS CLI.

程式是用 Python 寫的,可以透過 pip 直接安裝到自己的目錄下,官方說明支援 2.6.5+、2.7+、3.3+、3.4+,所以應該是不會有太多問題:

$ pip install aws-shell

第一次執行的時候放著讓他背景建立 index 會比較順。



可以看到功能相當強,甚至可以連到 AWS 上取得資料。

建議 GitHub 上的首頁說明部份都先看完,然後裝起來先測試玩看看,對於真的要用的時候會方便很多。

另外他執行時真的丟到 shell 去跑,所以你可以 pipe 出去處理,像是這樣:

ec2 describe-instances | jq .

新版 byobu 的 .screenrc

之前用的 Byobu 會吃 $HOME/.screenrc,但前陣子發現失效了 (我習慣把 screen 的 escape 換成 Ctrl-a + Ctrl-a,而非預設的 Ctal-a + a),研究後發現得用 .byobu/.screenrc 這邊,所以就用 symbolic link 連出來:

$ cd ~/.byobu; ln -s ../.screenrc


利用 MAC address 抓出網路攝影機 (AirBnB 事件後續的反制)

之前 AirBnB 的屋主在屋內安裝攝影機而打官司的事情繼續被討論:「Beware, houseguests: Cheap home surveillance cameras are everywhere now」。有人提出自救方法,作者使用 DropCam 與 Withings 的 MAC Address Prefix 抓出網路攝影機:「Detect and disconnect WiFi cameras in that AirBnB you’re staying in」。

由於 MAC address 不需要知道 WPA passphase,所以可以直接掃出來。作者提供的程式需要使用 airmon-ng 來掃無線網路。

另外作者有點出這個方法可以打掛透過無線網路的裝置 (像是 WiFi jammer),用在安全機制上 (也就是這些產品本來的設計) 未必有效,還是建議用有線網路接:

For the record, I’m well aware DropCam and Withings are also sold as baby monitors and home security products. The very fact this code exists should challenge you to reconsider the non-sane choice to rely on anything wireless for home security. More so, WiFi jammers - while illegal - are cheap. If you care, use cable.


It may be illegal to use this script in the US. Due to changes in FCC regulation in 2015, it appears intentionally de-authing WiFi clients, even in your own home, is now classed as ‘jamming’. Up until recently, jamming was defined as the indiscriminate addition of noise to signal - still the global technical definition. It’s worth noting here that all wireless routers necessarily ship with the ability to de-auth, as part of the 802.11 specification.

AWS 推出 Git Hook,阻擋 AWS 的 Key 被傳到 Git 上...

AWS 推出的工具,可以阻擋 AWS 的 Key 被傳到 Git 上:「awslabs/git-secrets」。可以看到說明:

git-secrets scans commits, commit messages, and --no-ff merges to prevent adding secrets into your git repositories. If a commit, commit message, or any commit in a --no-ff merge history matches one of your configured prohibited regular expression patterns, then the commit is rejected.


AWS 的 EC2 Run Command 功能支援 Linux Instance

也是 AWS 在年假前丟出來的功能:「EC2 Run Command Update – Now Available for Linux Instances」。

原先只能用在 Windows Instance 上,現在則支援 Linux Instance 了:

When we launched EC2 Run Command seven weeks ago (see my post, New EC2 Run Command – Remote Instance Management at Scale to learn more), I promised similar functionality for instances that run Linux. I am happy to be able to report that this functionality is available now and that you can start using it today.

跟一般 SSH 登入不一樣的地方在於這個功能可以被 AWS IAM 的系統稽核,所有透過這個功能下的指令都會被 AWS 記錄起來。