Forget root password of a Debian Machine & resetting it

I am writing this small post just because

• i forgot the root password of my debian machine
• didn’t find a through post that list all steps in one place and had to look at several ones at a time

The steps are as follows

I am quoting these lines from that post

Some Linux distribution, such as Ubuntu for instance, offer a specific boot menu entry where it is stated "Recovery Mode" or "Single-User Mode". If this is your case, selecting this menu entry will boot your machine into single user mode, you can carry on with the next part. If not, you might want to read this part.

Using GRUB, you can manually edit the proposed menu entry at boot time. To do so, when GRUB is presenting the menu list (you might need to press ESC first), follow those instructions:

• use the arrows to select the boot entry you want to modify.
• press e to edit the entry
• use the arrows to go to kernel line
• press e to edit this entry
• at the end of the line add the word single
• press ESC to go back to the parent menu
• press b to boot this kernel

The kernel should be booting as usual (except for the graphical splash screen you might be used to), and you will finally get a root prompt (sh#).

Here we are, we have gained root access to the filesystem, let's finally change the password.

According to the above words, we should be ok and we have access to the file system. At this state you run the command “passwd” and enter the new password.

If it worked with you then Thanks to the editor. If you got some problems like me, then keep reading.

Problem 1

After editing grub line and add the “single” keyword at the end of that line. I got it loading well until i was prompted for the root password for maintenance and give the ability to skip but by then i will be leaving runlevel 1 and entering runlevel 2 getting login/password prompt i am trying to skip.

To solve this problem do the following:

• Edit the grub line again and leave the keyword “single” there as before but add at the end as well these words “init=/bin/bash”
• exit edit mode
• press the button “b” while you have this modified grub line highlighted to start booting with this modified grub line

Voila, you have now access to shell as a root. run the command “passwd” and you should be fine entering the new desired password. If you got a problem, then continue reading.

Problem 2

Whenever i run the command “passwd” and re-enter the new password i get this error at the end

authentication token lock busy

If so, know that the problem is that you are accessing the system in read-only mode. In order to access it in read-write mode, do the following.

From the shell run this command

mount -o remount,rw /

after that run “passwd” command and this time you should have the ability to enter the new password

and live happily ever after

Factory Girl in Development

Some many developers use Factory Girl as a replacement to Fixtures and they depend on this gem in Test cases writing.

But Factory Girl can be very useful also in development and can be used in order to generate a bunch of dummy data with different specs for showing your work and reviewing all its details.

The problem we face is that Factory Girl can generate more records in tables that should have their data unchanged such as Countries table.

For example:

Factory.define :user do |f|
  f.association :country
end

Factory.define :job do |f|
  …
  f.association :user
end

Now, when we run this piece of code that generates 10 jobs

10.times { Factory.create(:job) }

we will get 10 countries auto-generated
violating the rule we wish to maintain which is having the countries table as it is

To workaround this problem without causing any changes in the code written previously, i came up with that solution

class Factory
  class << self
    alias_method :create_original, :create
    
    def create(name, overrides = {})
      if name.to_s == 'country'
        country = Country.first
        return country if country
      end

      create_original(name, overrides)
    end
  end
end

The logic introduced in the above script is simply adding a layer before creation that checks if the created object of certain type and if that type is desired to not be generated, we return the first entry we have in the DB else we do the normal creation

You can add this script in a file and load it in the development environment and use Factory Girl safely without fearing of generating data for tables that should remain as lookup tables

Enjoy :)

Factory Girl & Polymorphic Associations

Suppose you have a case like that

class Address < ActiveRecord::Base
  belongs_to :addressable, polymorphic => true
end

class Listing < ActiveRecord::Base
  has_one :address, as => :addressable
end

class Customer < ActiveRecord::Base
  has_one :address, as => :addressable
end

Now in your factories you will have something like that

Factory.define :listing do |f|
  f.association :address
end

since addressable is required, we choose it to be by default related to a customer unless else stated

Factory.define :address do |f|
  f.association :addressable, :factory => :customer
end

right now if you tried to use the Listing Factory, you will get an address associated with dummy customer and no effect on your side

How can this be fixed ?

Factory.define :listing do |f|
  f.after_build do |listing|
    listing.address = Factory.create(:address, :addressable => listing)
  end
end

This was the only solution i found after searching for a while
which is a good solution and doesn't need a lot of work to be done

sanitize gem issue

I have used ‘sanitize’ gem to remove HTML tags from entered text
the version i was using was ‘1.0.8’

After using it for a while, i found an issue in it where calling
Sanitize.clean(“’”) will return “#39;” while quote isn’t HTML character

Looking around for a reason for this issue, i found that this is a defect that was detected in older versions and that it is now fixed in version ‘1.1.0’

So anyone who has this issue can simply remove his installed gem and install the latest one

smtp 555 5.5.2 Syntax error (Net::SMTPFatalError)

This title was part of an error message i got while dealing with action_mailer

i looked everywhere for a reason for this error message and found so many reasons but none of them matched with my case

So i liked to share why i got this error. Simply because i was adding no recipients to my email. I know it is very weird to send an email without having a recipient but getting this error message i much more weird and strange

/usr/lib/ruby/1.8/net/smtp.rb:930:in `check_response': 555 5.5.2 Syntax error. 24sm123817eyx.21 (Net::SMTPFatalError)
        from /usr/lib/ruby/1.8/net/smtp.rb:899:in `getok'
        from /usr/lib/ruby/1.8/net/smtp.rb:842:in `rcptto'
        from /usr/lib/ruby/1.8/net/smtp.rb:834:in `rcptto_list'
        from /usr/lib/ruby/1.8/net/smtp.rb:833:in `each'
        from /usr/lib/ruby/1.8/net/smtp.rb:833:in `rcptto_list'
        from /usr/lib/ruby/1.8/net/smtp.rb:654:in `sendmail'
        from /usr/lib/ruby/gems/1.8/gems/actionmailer-2.3.2/lib/action_mailer/base.rb:683:in `perform_delivery_smtp'
        from /usr/lib/ruby/1.8/net/smtp.rb:526:in `start'
        from /usr/lib/ruby/gems/1.8/gems/actionmailer-2.3.2/lib/action_mailer/base.rb:681:in `perform_delivery_smtp'
        from /usr/lib/ruby/gems/1.8/gems/actionmailer-2.3.2/lib/action_mailer/base.rb:523:in `__send__'
        from /usr/lib/ruby/gems/1.8/gems/actionmailer-2.3.2/lib/action_mailer/base.rb:523:in `deliver!'
        from /usr/lib/ruby/gems/1.8/gems/actionmailer-2.3.2/lib/action_mailer/base.rb:395:in `method_missing'
        from test_sending_emails_in_ruby.rb:31 

this is the error message i got and it was solved when i added a recipient

Memory Leakage while using Mechanize

I was working on a task that scrape several web pages. After running this task for a while, i found that memory taken by my process is raising forever until it was about to eat all memory available of the server.

after some investigation regarding this matter, i knew that the problem was in my understanding to how mechanize agent works

let me explain with an example

agent = WWW::Mechanize.new
while(true)
page = agent.get(“www.example.com”)
end

in this example, memory will be consumed because mechanize keeps history within the agent, i looked in its documentation and found that there is a parameter which is called “max_history” which when set will fix this issue i think but didn’t try

also a fix to such issue, if you don’t need history is to write your code like that

while(true)
agent = WWW::Mechanize.new
page = agent.get(“www.example.com”)
end

That’s it, maybe this piece of information can be useful for someone facing this issue just like me

Install Mechanize On Debian

Installing mechanize gem on Debian should be as easy as running this command

gem install mechanize

but this won’t succeed unless you install these packages on your Debian machine

apt-get install libxml-dev libxslt1-dev

Once installed, gem will be installed seamlessly

Update:

if the above apt-get command didn't work with you and you got an error that package doesn't exist

try this new line

apt-get install libxml2-dev libxslt1-dev

as some packages names has changed