module Linux
  class User
    class << self
      # Generate an MD5 salt string
      def salt
        seeds = ('a'..'z').to_a
        seeds.concat( ('A'..'Z').to_a )
        seeds.concat( (0..9).to_a )
        seeds.concat ['/', '.']
        seeds.compact!
 
        salt_string = '$1$'
        8.times { salt_string << seeds[ rand(seeds.size) ].to_s }
 
        salt_string
      end
 
      # Crypt a password suitable for use in shadow files
      def crypt( string )
        string.crypt( self.salt )
      end
    end
  end
end

And the spec

require File.dirname(__FILE__) + '/../spec_helper'
 
describe Linux::User do
  describe "generating shadow passwords" do
    it "should generate a salt for crypt" do
      salt = Linux::User.salt
      salt.length.should be(11)
      salt.should match(/^\$1\$[a-zA-Z0-9\.\/]{8}$/)
    end
 
    it "should generate a shadow password" do
      pass = Linux::User.crypt( 'secret' )
      pass.should match(/^\$1\$[a-zA-Z0-9\.\/]{8}\$[a-zA-Z0-9\.\/]{22}$/)
      pass.length.should be(34)
    end
  end
end

HTH

So in panic I googled and read several man pages, coming to the following conclusion that worked quite well:

1. Find the offending commit with git log or git log -p, not the revision number prior to the catastrophic change.
2. View the file at that point in time with git show SHA-ID:path/to/file
3. Replace current copy with git show SHA-ID:path/to/file > path/to/file
4. Verify the damage has been undone with git diff
5. Commit
6. Breathe

Git is a double edged sword, it is extremely powerful and useful, but can be a real pain in the behind. I love git, and will not easily be convinced to move to something else.

So I decided to quickly cook up this little bash script that I run from my top level working directory, and have it clear all the log files, in all my Rails projects.

Hope it helps.

Basically search through the postfix maillog for a pattern, extract the postfix message id from each matched line, and then search through the log file for each corresponding line.

This rebuilds your original search with some more context, and makes it a snap to trace a message through its lifecycle…

I had the fortunate pleasure of guest lecturing at the Tshwane University of Technology a couple of weeks ago on Capistrano. The class was a group of final year students that are just learning Rails. The lecturer had already covered Capistrano with the students to some degree and called me in to get them excited and show them how it works in the wild.

The presentation itself doesn’t really do the session justice, it was driven more by the Q&A session afterwards.

I really enjoyed this session in particular since the students really interacted well with me and came up with some good questions and counter-arguments. I think one of the successes of the lecture was staying as far away from Rails as possible, and just focus on the dynamics of Capistrano and what an awesome tool it really is.

I’d also like to thank Jamis for this awesome tool, and all the members on the Capistrano Google Group who tirelessly help other people out with their deployment woes. Several members of the group also reviewed the presentation before my class, giving valuable feedback that I could convey to the students as well.

Capistrano Presentation @ TUT (20080529)

Try it, you’ll love it….

Posts to come on Xen, Ruby & Ruby on Rails, Python & Django and killing spam…

Back to business, this blog was conceptualized to focus on some of the real benefits of using open-source software in business. Not the kind of business that Novell and IBM try to make of open-source, but small businesses seeking to gain an advantage in a very competitive market space.

Today this power shined through dramatically again, through a little piece of software called policyd. Policyd is a greylisting service built for Postfix (the ever so popular MTA) and allows anyone with a mail server to implement greylisting, blacklisting, whitelisting and a host of other features in the fight against spam.

I needed to change the way policyd used the MySQL backend, and in doing so it meant editing C code that I know nothing about. It turn out to be relatively easy when you apply common sense and all the knowledge you’ve gained from coding in interpreted languages all your life. So I need to be able to prefix the tables in the MySQL database used by policyd in order to prevent clashes with other mail-related software sharing the same database. It is scheduled for the next major release version, but I needed this feature today. So after skimming through some of the .c files I realized that this wouldn’t be a too big feat…

It took me an hour, more or less, to complete modify every single SQL statement in the code, add new configuration directives and create a patch that I submitted to the policyd-users list for testing. Currently I’m still testing as well, and everything looks 100%.

This allows me to actually adapt software in an hour to fit my needs. This is the real power of open source. Imagine the time and effort it would take to consult with the developers of proprietary software to get such a minor change done. Even if I push my rates per hour up 10 fold, it would not compare to the cost of getting proprietary software adapted quickly and easily.

And in the true spirit of open-source (blatantly ignoring any licenses) the patch is available on the list archive pages of the policyd-users mailing list at SourceForge. If you need it, grab it here: http://sourceforge.net/mailarchive/forum.php?thread_id=9613438&forum_id=46105

Absolutely amazing, what will we see next…?