synatic|blog by Benedikt Deicke

Typing SSH passwords again and again can be a real pain. For example: Lately I started to use Capistrano to deploy my rails applications. If I want to set up the maintenance-page on the server I’ll type cap deploy:web:disable which of course prompts me for the SSH password. Then I want to deploy my application with cap deploy and again will be prompted for the password. Finally I have to cap deploy:web:enable to remove the maintenance page which – as mindful readers might have guessed already – prompts for the password. This was just one reason for me to set up SSH authentication keys. At first I was a little worried that setting it up might be a bit complicated. Luckily I was disabused. If you want to switch to key based authentication too follow these simple steps:

Key generation

The first thing you need is – of course – a pair of keys: your private key and the associated public key. To generate both fire up our favorite shell (for me it’s bash) and type:

   1  ssh-keygen

This will generate both keys and ask you where to store it. Usually the default would be something like ~/.ssh/id_rsa. Simply accept the default by pressing return. Next you’ll have to enter a password for your key and confirm it. Afterwards you’ve to tell the server to accept your key on authentication. Do so by uploading the public key to the server.

   1  scp ~/.ssh/id_rsa.pub yourserver.com:~/.ssh/authenticated_keys2

If you want to add multiple keys, be sure to append it to the authenticated_keys2 file and don’t overwrite it.

First login

That’s all you have to do to switch to key based SSH authentication. Try to log in as usual by typing:

   1  ssh yourserver.com

This will prompt you for your key’s password and log you in to your server afterwards. “But wait! I’m still having to type my password every time I want to log in!” you shout, and you’re right – up to now. What you need to do is running ssh-agent, adding your key and typing your password. ssh-agent will then ask for the password and store it until you shut it down. You’ll have to do this everytime you open up a new shell or put the commands into your i.e. ~/.bash_profile. Quite comfortable but we can do better.

Keychain

There is a nice little tool called keychain that will smooth the process a little for you. It’s originally developed by the Gentoo people but it’s available on other linux distributions (as well as Mac OS X), too. Simply install it by typing your system’s equivalent to

   1  # Gentoo
   2  emerge keychain
   3  # Debian
   4  aptitude install keychain

and it’ll be available in no time. To set it up you need to put these two lines in our ~/.bash_profile:

   1  keychain ~/.ssh/id_rsa
   2  source ~/.keychain/$HOSTNAME-sh

That’s it. The first time you open up a shell keychain will start ssh-agent, prompt you for your keys password and remember the running ssh-agent for all new shells. On your next SSH authentication no more password typing is required. Wasn’t complicated at all, was it?

Update: Thanks to Michael for pointing out that the public key file is named id_rsa.pub instead of id_rsa. Fixed it.

I’ve had a great weekend again, seeing Nightwish doing two amazing shows. First one on saturday in Leipzig, the second one in Frankfurt on monday. I took several pictures and uploaded a selection of them to the Nightwish.com Gallery:

• Photos of the Leipzig show on saturday
• Photos of the Frankfurt show on monday

To give you an idea, here are some of the best ones:

I’m a total moron when it comes to web- and screendesign. I totally lost the ability to build visually appealing websites (or maybe my demands just grow) over the last few years. Unfortunately a good looking design is a must for every website or -application. I’ve some ideas in mind that I’d like to realize. To do so I definitely need help! As a result I’m looking for a

Web-/Screendesigner

for cooperation on these (and maybe even more) projects. Knowledge of (x)html, css, and javascript is a plus but not necessarily required. So, if you’re experienced in designing websites please contact me by mail using benedikt at synatic dot net or comment below.

I’m looking forward to your message! :-)

Thanks!

I just played a mms-stream using mplayer in the console. After it was done I read this in the console:

(Looks like this is my shortest blog entry ever … ;-))

There is a great article by Jason Long on Vitamin called ‘Streamline your forms with widgets’. In his article Jason Long describes a nice looking way to clean up a lot of checkboxes into multiple dropdown widgets. What I really liked was the idea to have some summary about the selected items next to the title of the dropdown widgets. Unfortunately he didn’t implement the updating function but just mentioned it as a possible extension. In addition he pointed out that “Any Fuel” would be much easier to read than “Fuel (Gasoline, Diesel, Alternative)”. As I was in the right mood for some Javascript I implemented the missing functionality.

At first I added four little lines to the top of the toggleDropdown() function. This little snippet checks weather the panel is currently visible (so the function was toggled to hide the panel again) and calls the updateTitle() function.

   1  function toggleDropdown(panel) 
   2  {
   3    panel = $(panel);
   4    if(panel.visible()) {
   5      updateTitle(panel);
   6    }
   7  
   8    // toggle the requested one
   9    Element.toggle(panel);
  10       
  11    // then hide all of the others so that only
  12    // one (at most) is open at a time
  13    $$('body .dd_option_panel').each(function(node){
  14      if (node != $(panel)) {
  15        Element.hide(node);
  16      }
  17    });  
  18  }

To do the actual updating of the title I used Prototype’s nifty little DOM traversal toolkit. It provides methods such as Element#select(), Element#up(), Element#down(), Element#previous() and Element#next(). All of can be supplied with a selector, similar to those in CSS.

First I select all child elements of type “input” and check their value. If the value matches “on” the checkbox is selected and I travel down to the next “label”-element to push it’s content into an array. Afterwards I check the size of this array and decide how to change the title. If none of the checkboxes are selected I add “No ” to the title and don’t display the list of the selected values. Accordingly if all are selected I prepend “Any ”. Otherwise I leave the title as it is and update the list behind it by joining the elements of the array into a string. To prevent titles such as “Any Any No Any Fuel” I clean up the title by removing either Any or No in front of the title using String#gsub().

   1  function updateTitle(panel)
   2  {
   3    selected = new Array();
   4    panel.select('input').each(function(box){
   5      if(box.getValue() == 'on') {
   6        selected.push(box.next('label').innerHTML);
   7      }
   8    });
   9       
  10    inner = panel.previous(".inner");
  11    title = inner.innerHTML.gsub(/^([Any|No])/, '');
  12    
  13    if(selected.length == 0) {
  14      inner.update('No ' + title);
  15      inner.down(".light").update('');
  16    } else if(selected.length == panel.select('label').length) {
  17      inner.update('Any ' + title);
  18      inner.down('.light').update('');
  19    } else {
  20      inner.update(title);
  21      inner.down('.light').update('(' + selected.join(', ') + ')');
  22    }
  23  }

In order to get correct titles right from the beginning I update all titles after the page loaded.

   1  Event.observe(window, 'load', function(event) {
   2    $$('body .dd_option_panel').each(function(panel) {
   3      updateTitle(panel);
   4    });
   5  });

That’s it! Click here to see the changed example.

Of course all the credits for the original implementation, graphics, and idea go to Jason Long.