Challenge everything!

http://www.ruanyifeng.com/blog/2008/12/a_visual_guide_to_version_control.html

from http://www.junauza.com/2008/06/20-great-quotes-from-richard-m-stallman.html

I have here a collection of 20 of my favorite quotes from the famous free software evangelist and living legend Richard M. Stallman. I hope you will all like this one. Here it goes:

1- "I could have made money this way, and perhaps amused myself writing code. But I knew that at the end of my career, I would look back on years of building walls to divide people, and feel I had spent my life making the world a worse place."

2- "When I do this, some people think that it’s because I want my ego to be fed, right? Of course, I’m not asking you to call it "Stallmanix"!"

3- "I’m always happy when I’m protesting."

4- "Geeks like to think that they can ignore politics, you can leave politics alone, but politics won’t leave you alone."

5- "People sometimes ask me if it is a sin in the Church of Emacs to use vi. Using a free version of vi is not a sin; it is a penance. So happy hacking."

6- "If programmers deserve to be rewarded for creating innovative programs, by the same token they deserve to be punished if they restrict the use of these programs."

7- "Fighting patents one by one will never eliminate the danger of software patents, any more than swatting mosquitoes will eliminate malaria."

8- "People said I should accept the world. Bullshit! I don’t accept the world."

9- "Giving the Linus Torvalds Award to the Free Software Foundation is a bit like giving the Han Solo Award to the Rebel Alliance."

10- "Would a dating service on the net be ‘frowned upon’ . . . ? I hope not. But even if it is, don’t let that stop you from notifying me via net mail if you start one."

11- "Once GNU is written, everyone will be able to obtain good system software free, just like air."

12- "If you want to accomplish something in the world, idealism is not enough–you need to choose a method that works to achieve the goal. In other words, you need to be "pragmatic."

13- "No person, no idea, and no religion deserves to be illegal to insult, not even the Church of Emacs."

14- "Today many people are switching to free software for purely practical reasons. That is good, as far as it goes, but that isn’t all we need to do! Attracting users to free software is not the whole job, just the first step."

15- "If in my lifetime the problem of non-free software is solved, I could perhaps relax and write software again. But I might instead try to help deal with the world’s larger problems. Standing up to an evil system is exhilarating, and now I have a taste for it."

16- "I see nothing unethical in the job it does. Why shouldn’t you send a copy of some music to a friend?"

17- "’Free software’ is a matter of liberty, not price. To understand the concept, you should think of ‘free’ as in ‘free speech,’ not as in ‘free beer’."

18- "For personal reasons, I do not browse the web from my computer. (I also have not net connection much of the time.) To look at page I send mail to a demon which runs wget and mails the page back to me. It is very efficient use of my time, but it is slow in real time."

19- "Playfully doing something difficult, whether useful or not, that is hacking."

20- "Copying all or parts of a program is as natural to a programmer as breathing, and as productive. It ought to be as free."

If you have a favorite Richard M. Stallman quote, feel free to share it to us.

摘自：http://linuxproblem.org/art_9.html

Your aim

You want to use Linux and OpenSSH to automize your tasks. Therefore you need an automatic login from host A / user a to Host B / user b. You don’t want to enter any passwords, because you want to call ssh from a within a shell script.

How to do it

First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:

a@A:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa): 
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A

Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):
a@A:~> ssh b@B mkdir -p .ssh
b@B's password: 

Finally append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:
a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'
b@B's password: 

From now on you can log into B as b from A as a without password:
a@A:~> ssh b@B hostname
B

A note from one of our readers:  Depending on your version of SSH you might also have to do the following changes:

Put the public key in .ssh/authorized_keys2
Change the permissions of .ssh to 700
Change the permissions of .ssh/authorized_keys2 to 640