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20140307-1 选题
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10 ssh options for a Secure shell for Safe Data Communication
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================================================================================
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A system administrator may have managed more than 1 servers. Then those servers may located in different places. Visiting the servers one by one may not the best way to manage them. Then a remote method can be an effective way to manage them. One of the common aplication for remote activity is **SSH**.
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### What is SSH ###
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**SSH or Secure Shell** is a cryptographic network protocol. The data through this protocol will be encrypted to ensure that no one can read if the data leaked in the middle. To use SSH, the destination machine should have a SSH server application installed because **SSH is a client-server model**. SSH is usually used when you want to remote hosts in a secure way over the insecure network such as the Internet.
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### Installing SSH ###
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Modern Linux should have installed SSH by default. If its not, we can install it manually. The easiest way to install SSH is through your Linux package manager.
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### On Debian / Ubuntu Linux based : ###
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#### Install ssh-client ####
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$ sudo apt-get install openssh-client
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#### Install ssh-server ####
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$ sudo apt-get install openssh-server
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### On RedHat / CentOS Linux based : ###
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# yum install openssh-server openssh-clients
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Once SSH is installed we can check it by typing **ssh** from your Linux console.
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### Using SSH ###
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SSH provides a lot of options to be used. In this article we will cover some options that may useful in day-to-day operations.
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#### 1. Run SSH without no options ####
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A common way to use SSH is without any options. Just type “**ssh** ”. Here’s a sample :
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$ ssh 192.168.0.103
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When the first time you connect to destination host, ssh will confirm you about the authenticity of the destination host. If you answer No****, then SSH will not continue while **if you said Yes**, SSH will continue.
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The next time you login into the same host, SSH will not ask you a confirmation. The authenticity oft the host by default is saved under /home/user/.ssh folder in every user.
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#### 2. Specify a username for login ####
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By default, ssh will try to connect using active user as a username. On the previous command, ssh will try to login into the server using a username named pungki. This is because user pungki on the client side, is running ssh client.
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What about if in the destination host, there is no user named pungki? Then you must supply a username that exist in the destination host. To specify the username from the beginning, use -l option
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$ ssh -l leni 192.168.0.103
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We can also type like this :
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$ ssh leni@192.168.0.0103
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#### 3. Specify the port ####
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**SSH default port is 22**. Most of modern Linux are open port 22. If you run ssh without defining a port, then ssh will direct the request via port 22.
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But some system administrator may changed the default SSH port. Let say that the port now is 1234. To contact that host, use **-p** option followed by SSH port.
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$ ssh 192.168.0.103 -p 1234
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To change the port number, we need to modify the **/etc/ssh/ssh_config**.
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Find the line :
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Port 22
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Change it into another port, for example above, is 1234. Then restart the SSH service.
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#### 4. Request compression on every data ####
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With this option, all data which sent and received via SSH will be compressed. The data still encrypted. To use compression with SSH, use **-C** option.
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$ ssh -C 192.168.0.103
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This option will be useful if your connection is slow, such as using a modem. But when you are using a fast connection such as LAN or higher, than compression will be slow down your transfer rate.
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The level of compression can be controlled using **-o** option followed by **CompressionLevel** option. But this option will only applied for SSH-1.
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#### 5. Define a cipher algorithm ####
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SSH provides some cipher algorithms to be used. These algorithms can be seen inside **/etc/ssh/ssh_config or ~/.ssh/config file** (if exist).
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Let say you want to use **blowfish** algorithm for encrypting your SSH session. Then you can put this line into your **/etc/ssh/ssh_config or ~/.ssh/config** file :
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Cipher blowfish
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By default, SSH will use 3des algorithm
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#### 6. Turn on debug mode ####
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For some reason, we may want to debug the SSH connection that we want to create. SSH provides **-v** option to do this.
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$ ssh -v 192.168.0.103
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#### 7. Bind source address ####
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If your client has more than 2 IP Address, you might not know which IP Address is used to create a connection to the SSH server.
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To solve this situation, we can use -b option which will bind an IP Address to SSH connection. This IP Address will be used as the source address of the connection.
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$ ssh -b 192.168.0.200 -l leni 192.168.0.103
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On the server side, we can check the established connection to the server using netstat. We see that 192.168.0.200 connection is established.
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#### 8. Use other configuration file ####
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By default, ssh will use a ssh configuration file which located in **/etc/ssh/ssh_config**. This file is applied to system wide. If you want to apply particular setting to specific user, you should put it in **~/.ssh/config** file. If you don’t see it, you can create it.
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Here’s a sample of a custom **ssh_config**. This config is located in **/home/pungki directory**.
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Host 192.168.0.*
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ForwardX11 yes
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PasswordAuthentication yes
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ConnectTimeout 10
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Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
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Protocol 2
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HashKnownHosts yes
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To use a specific config file, we can use **-F** option.
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$ ssh -F /home/pungki/my_ssh_config 192.168.0.101
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### 9. Use SSH X11 Forwarding ###
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For some reason, you may want to display a X11 application on the server into your client computer. SSH provides **-X** option to do this. But in order to enable this feature, we need some preparation. Here’s the settings
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On the server side, you need to enable line **ForwardX11 yes or X11Forward yes** in **/etc/ssh/ssh_config**. Then restart your SSH server.
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Then on the client side, type **ssh -X user@host** :
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$ ssh -X leni@192.168.0.101
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Once you have logged on, you can check it by typing :
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$ echo $DISPLAY
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You should see something like
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localhost:10:0
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Then to run an application, just type the command of the application. Let say you want to run xclock application. Then type :
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$ xclock
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When it run, actually you are running the xclock application on the remote system, but display it on your local system.
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#### 10. Trusted X11 Forwading ####
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If you pretty sure that your network is secure, then you may want to use **Trusted X11 Forwarding**. This mean that the remote X11 clients will have full access to the original X11 display. To use this option, we can use **-Y** option.
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$ ssh -Y leni@192.168.0.101
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### Conclusion ###
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We believe that SSH is used in wide-range area. Security and flexibility is one of the SSH offer to the user. As usual we can always type **man ssh** and **man ssh_config** to display its manual pages and explore more detail.
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--------------------------------------------------------------------------------
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via: http://linoxide.com/linux-command/learn-ssh-connection-options/
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译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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51
sources/Interesting facts about Raspberry Pi.md
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Interesting facts about Raspberry Pi
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================================================================================
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Raspberry Pi celebrated its second birthday last week. Since its debut on February 29, 2012, Raspberry Pi has ushered in a whole new generation of tiny, inexpensive, single-board computers. Numerous Raspberry Pi based DIY project ideas are popping up over the web, and there are many use cases of Raspberry Pi as low-cost learning media in the developing world. Celebrating its second birthday, I am going to share in this post several **interesting facts about Raspberry Pi**.
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1. [100,000 Raspberry Pi boards][1] were sold on the first day of launch, and more than [2.5 million units][2] of them have been sold so far worldwide.
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2. Initial batches of Raspberry Pi boards were made in Taiwan and China, but now all Raspberry Pi boards being sold are [manufactured in the UK][3].
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3. Raspberry Pi is overclockable (by entering so-called [turbo mode][4]). You can change [overclocking/overvolting options][5] either at run-time with raspi-config tool, or at boot-time by editing boot-time parameters in /boot/config.txt. Changing overclocking/overvolting options does not void your warranty.
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4. Raspberry Pi does not come with MPEG-2 decoder. Adding a blanket license for MPEG-2/VC-1 codecs to Raspberry Pi would [increase its board price by 10%][6]. Instead, you can [purchase MPEG-2/VC-1 license keys][7] only if you need to. Purchased licenses are tied to individual Raspberry Pi boards.
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5. You [cannot run Windows 8][8] on Raspberry Pi (ARMv6) as Windows 8 requires an ARMv7 or higher processor. Likewise, you cannot run Ubuntu on Raspberry Pi as Ubuntu only supports [ARMv7 or higher][9].
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6. [Origin][10] of the name Rapberry Pi: "Raspberry" originates from the fruit-based naming tradition for microcomputers in old days. "Pi" refers to "Python" because Python was one of the first programs ported to run on Raspberry Pi.
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7. Raspberry in the [Raspberry Pi logo][11] is actually 3D [Buckminsterfullerene][12] (or bucky-ball) which has a total of 32 faces. 11 of them are visible in the logo. Co-incidentally, Raspberry Pi has a 32-bit ARM11 processor on board.
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8. Methematica, a popular computational software program commercially available, [comes bundled for free][13] on Rapsberry Pi.
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9. (thanks to garry grant) The biggest Kickstarter project which is based on Raspberry Pi is [Kano][14], where the goal is to delivery a computer/coding kit which can help people of all ages make a computer themselves. The project has garnered $1,522,160 from 13,387 backers.
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10. According to [Rastrack.co.uk][15], the country where RaspberryPi is the most popular is UK.
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That is all. If you know any interesting fact about Raspberry Pi, feel free to chime in.
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--------------------------------------------------------------------------------
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via: http://xmodulo.com/2014/03/interesting-facts-raspberry-pi.html
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译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[1]:http://www.zdnet.com/we-thought-wed-sell-1000-the-inside-story-of-the-raspberry-pi-7000009718/
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[2]:http://www.raspberrypi.org/archives/6299
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[3]:http://www.raspberrypi.org/archives/5016
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[4]:http://www.raspberrypi.org/archives/2008
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[5]:http://elinux.org/RPi_config.txt#Overclocking_options
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[6]:http://www.raspberrypi.org/archives/1839
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[7]:http://www.raspberrypi.com/
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[8]:http://www.gamesindustry.biz/articles/digitalfoundry-inside-raspberry-pi
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[9]:https://wiki.ubuntu.com/ARM
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[10]:http://www.techspot.com/article/531-eben-upton-interview/
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[11]:http://www.raspberrypi.org/archives/221
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[12]:http://en.wikipedia.org/wiki/Buckminsterfullerene
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[13]:http://blog.stephenwolfram.com/2013/11/putting-the-wolfram-language-and-mathematica-on-every-raspberry-pi/
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[14]:https://www.kickstarter.com/projects/alexklein/kano-a-computer-anyone-can-make
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[15]:http://www.rastrack.co.uk/
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162
sources/What is good video editing software on Linux.md
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What is good video editing software on Linux?
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================================================================================
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A video editor allows you to handle various post-production video editing jobs which typically involve arranging, cutting, pasting, trimming, and otherwise enhancing (e.g., adding effects to) video clips through the timeline interface. In modern video editing software, things like multi-codec import/transcoding, non-linear video editing, or even HD video support are pretty much standard nowadays.
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In this post, I am going to show **11 popular video editing software available on Linux**. I will not cover subjective merits such as usability or interface design, but instead highlight notable features of each video editor. If you have tried any particular video editor listed here, feel free to share your experience or opinion.
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### 1. Avidemux ###
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- License: GNU GPL
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- Cross-platform (Linux, BSD, MacOS X, Windows)
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- Supports both GUI and command-line modes
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- Support for JavaScript (thanks to SpiderMonky JavaScript engine)
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- Built-in subtitle processing
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- Official website: [http://fixounet.free.fr/avidemux][1]
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### 2. Blender ###
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- License: GNU GPL v3+
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- Cross-platform (Linux, BSD, MacOS X, Windows)
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- Specialized in creating 3D modeling and animation
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- Support for image/video compositing
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- Video/audio effects and transitions
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- Official website: [http://www.blender.org][2]
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### 3. Cinelerra-CV ###
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- License: GNU GPL
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- Community edition of Cinelerra video editor
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- Support for video compositing
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- Drag and drop files from file manager
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- OpenGL-driven GPU acceleration for video playback
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- Video/audio effects and transitions
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- Direct capture from camcorders
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- Cross-platform (Linux and Windows)
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- Official website: [http://cinelerra.org][3]
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### 4. Flowblade ###
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- License: GNU GPL v3
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- Support for multiple file types based on FFmpeg
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- Drag and drop files from file manager
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- Support for video and image compositing
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- Image and audio effects
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- Automatic clip placement on the timeline
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- Official website: [https://code.google.com/p/flowblade/][4]
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### 5. Jahshaka ###
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- License: GNU GPL
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- Cross-platform (Linux, MacOS X, Windows)
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- Support for 2D/3D animation effects and video composting
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- Support for collaborative editing (e.g., editing server and centralized database)
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- Media/asset management
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- GPU based effects
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- Official website: [http://www.jahshaka.com][5]
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### 6. Kdenlive ###
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- License: GNU GPL v2+
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- Video editor for the KDE desktop
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- Support for multiple file types based on FFmpeg
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- Video/audio effects and transitions
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- Ability ot mix video, audio and still images from different sources
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- Video capture from cameras, webcams, Video4Linux devices or X11 screen
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- Export to Internet video sharing sites such as YouTube, Dailymotion or Vimeo
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- Official website: [http://www.kdenlive.org][6]
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### 7. Lightworks ###
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- License: Freemium
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- Cross-platform (Linux, BSD, MacOS X, Windows)
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- Multi-language support
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- GPU-accelerated real-time video effects and composting
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- Official website: [http://www.lwks.com][7]
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### 8.LiVES ###
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- License: GNU GPL
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- Cross-platform (Linux, BSD, MacOS X, Solaris)
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- Multi video formats via mplayer
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- Extendable video/audio effects via plugins
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- Support for remote control via OSC protocol
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- Video capture from FireWire cameras and TV cards
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- Lossless backup and crash recovery
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- Support for clip import from YouTube
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- Official website: [http://lives.sourceforge.net][8]
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### 9. OpenShot ###
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- License: GNU GPL v3
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- Support for multiple file types based on FFmpeg
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- Drag and drop files from file manager
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- Support for 2D titles (thanks to Inkscape) and 3D-animated titles (thanks to Blender)
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- Digital zooming
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- Animated video transition with preview
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- Support for video compositing and watermark images
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- Scrolling eding credits or texts
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- Official website: [http://www.openshot.org][9]
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### 10. Pitivi ###
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- License: GNU LGPL
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- Video import, conversion and rendering powered by GStreamer Editing Service
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- Video/audio effects and transitions
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- Support for keyframes and video compositing
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- Detachable UI
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- Multi-language support (thanks to GNOME integration)
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- Official website: [http://www.pitivi.org][10]
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### 11. Shotcut ###
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- License: GNU GPL
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- Cross-platform (Linux, MacOS X, Windows)
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- Support for multiple file types based on FFmpeg
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- Customizable UI via dockable panels
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- Multi-format timeline (e.g., with different resolutions and frame rates)
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- Video capture from webcam, HDMI, IP streams and X11 screen
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- Drag and drop files from file manager
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- GPU-assisted image processing with OpenGL
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- Official website: [http://www.shotcut.org][11]
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--------------------------------------------------------------------------------
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via: http://xmodulo.com/2014/03/good-video-editing-software-linux.html
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译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[1]:http://fixounet.free.fr/avidemux/
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[2]:http://www.blender.org/
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[3]:http://cinelerra.org/
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[4]:https://code.google.com/p/flowblade/
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[5]:http://www.jahshaka.com/
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[6]:http://www.kdenlive.org/
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[7]:http://www.lwks.com/
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[8]:http://lives.sourceforge.net/
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[9]:http://www.openshot.org/
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[10]:http://www.pitivi.org/
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[11]:http://www.shotcut.org/
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