Can't install MySQL gem

On Ubuntu/Debian and other distributions using aptitude:

sudo apt-get install libmysql-ruby libmysqlclient-dev

If the above command doesn't work because

libmysql-ruby

cannot be found, the following should be sufficient:

sudo apt-get install libmysqlclient-dev

On Red Hat/CentOS and other distributions using yum:

sudo yum install mysql-devel

On Mac OS X with Homebrew:

brew install mysql

Making Devise to response in json

Login Code

class SessionsController < DeviseController
  prepend_before_filter :require_no_authentication, :only => [ :new, :create ]
  prepend_before_filter :allow_params_authentication!, :only => :create
  prepend_before_filter { request.env["devise.skip_timeout"] = true }

  prepend_view_path 'app/views/devise'

  # GET /resource/sign_in
  def new
    self.resource = resource_class.new(sign_in_params)
    clean_up_passwords(resource)
    respond_with(resource, serialize_options(resource))
  end

  # POST /resource/sign_in
  def create
    self.resource = warden.authenticate!(auth_options)
    set_flash_message(:notice, :signed_in) if is_navigational_format?
    sign_in(resource_name, resource)

        respond_to do |format|
                format.json { render :json => resource, :status => :ok }
                format.html { respond_with resource, :location => after_sign_in_path_for(resource) } 
        end
  end

  # DELETE /resource/sign_out
  def destroy
    redirect_path = after_sign_out_path_for(resource_name)
    signed_out = (Devise.sign_out_all_scopes ? sign_out : sign_out(resource_name))
    set_flash_message :notice, :signed_out if signed_out && is_navigational_format?

    # We actually need to hardcode this as Rails default responder doesn't
    # support returning empty response on GET request
    respond_to do |format|
      format.all { head :no_content }
      format.any(*navigational_formats) { redirect_to redirect_path }
    end
  end


  protected

  def sign_in_params
    devise_parameter_sanitizer.sanitize(:sign_in)
  end

  def serialize_options(resource)
    methods = resource_class.authentication_keys.dup
    methods = methods.keys if methods.is_a?(Hash)
    methods << :password if resource.respond_to?(:password)
    { :methods => methods, :only => [:password] }
  end

  def auth_options
    { :scope => resource_name, :recall => "#{controller_path}#new" }
  end
end

#config/routes (notice custom controllers)
devise_for :users, :path => '', :controllers => {:sessions => 'sessions', :registrations => 'registrations'} 

Registration Code 

#app/controllers/registrations_controller.rb
class RegistrationsController < DeviseController
  prepend_before_filter :require_no_authentication, :only => [ :new, :create, :cancel ]
  prepend_before_filter :authenticate_scope!, :only => [:edit, :update, :destroy]

  before_filter :configure_permitted_parameters

  prepend_view_path 'app/views/devise'

  # GET /resource/sign_up
  def new
    build_resource({})
    respond_with self.resource
  end

  # POST /resource
  def create
    build_resource(sign_up_params)

    if resource.save
      if resource.active_for_authentication?
        set_flash_message :notice, :signed_up if is_navigational_format?
        sign_up(resource_name, resource)
        respond_with resource, :location => after_sign_up_path_for(resource)
      else
        set_flash_message :notice, :"signed_up_but_#{resource.inactive_message}" if is_navigational_format?
        expire_session_data_after_sign_in!
        respond_with resource, :location => after_inactive_sign_up_path_for(resource)
      end
    else
      clean_up_passwords resource

      respond_to do |format|
        format.json { render :json => resource.errors, :status => :unprocessable_entity }
        format.html { respond_with resource }
      end
    end
  end

  # GET /resource/edit
  def edit
    render :edit
  end

  # PUT /resource
  # We need to use a copy of the resource because we don't want to change
  # the current user in place.
  def update
    self.resource = resource_class.to_adapter.get!(send(:"current_#{resource_name}").to_key)
    prev_unconfirmed_email = resource.unconfirmed_email if resource.respond_to?(:unconfirmed_email)

    if update_resource(resource, account_update_params)
      if is_navigational_format?
        flash_key = update_needs_confirmation?(resource, prev_unconfirmed_email) ?
          :update_needs_confirmation : :updated
        set_flash_message :notice, flash_key
      end
      sign_in resource_name, resource, :bypass => true
      respond_with resource, :location => after_update_path_for(resource)
    else
      clean_up_passwords resource
      respond_with resource
    end
  end

  # DELETE /resource
  def destroy
    resource.destroy
    Devise.sign_out_all_scopes ? sign_out : sign_out(resource_name)
    set_flash_message :notice, :destroyed if is_navigational_format?
    respond_with_navigational(resource){ redirect_to after_sign_out_path_for(resource_name) }
  end

  # GET /resource/cancel
  # Forces the session data which is usually expired after sign
  # in to be expired now. This is useful if the user wants to
  # cancel oauth signing in/up in the middle of the process,
  # removing all OAuth session data.
  def cancel
    expire_session_data_after_sign_in!
    redirect_to new_registration_path(resource_name)
  end

  protected

  # Custom Fields
  def configure_permitted_parameters
    devise_parameter_sanitizer.for(:sign_up) do |u|
      u.permit(:first_name, :last_name,
        :email, :password, :password_confirmation)
    end
  end

  def update_needs_confirmation?(resource, previous)
    resource.respond_to?(:pending_reconfirmation?) &&
      resource.pending_reconfirmation? &&
      previous != resource.unconfirmed_email
  end

  # By default we want to require a password checks on update.
  # You can overwrite this method in your own RegistrationsController.
  def update_resource(resource, params)
    resource.update_with_password(params)
  end

  # Build a devise resource passing in the session. Useful to move
  # temporary session data to the newly created user.
  def build_resource(hash=nil)
    self.resource = resource_class.new_with_session(hash || {}, session)
  end

  # Signs in a user on sign up. You can overwrite this method in your own
  # RegistrationsController.
  def sign_up(resource_name, resource)
    sign_in(resource_name, resource)
  end

  # The path used after sign up. You need to overwrite this method
  # in your own RegistrationsController.
  def after_sign_up_path_for(resource)
    after_sign_in_path_for(resource)
  end

  # The path used after sign up for inactive accounts. You need to overwrite
  # this method in your own RegistrationsController.
  def after_inactive_sign_up_path_for(resource)
    respond_to?(:root_path) ? root_path : "/"
  end

  # The default url to be used after updating a resource. You need to overwrite
  # this method in your own RegistrationsController.
  def after_update_path_for(resource)
    signed_in_root_path(resource)
  end

  # Authenticates the current scope and gets the current resource from the session.
  def authenticate_scope!
    send(:"authenticate_#{resource_name}!", :force => true)
    self.resource = send(:"current_#{resource_name}")
  end

  def sign_up_params
    devise_parameter_sanitizer.sanitize(:sign_up)
  end

  def account_update_params
    devise_parameter_sanitizer.sanitize(:account_update)
  end
end 

Peer authentication failed for user “postgres”, when trying to get pgsql working with rails

sudo nano /etc/postgresql/9.1/main/pg_hba.conf

local   all             postgres                                peer

Should be

local   all             postgres                                md5

Peer authentication

The peer authentication method works by obtaining the client's
  operating system user name from the kernel and using it as the allowed
  database user name (with optional user name mapping). This method is
  only supported on local connections. 

Password authentication

The password-based authentication methods are md5 and password. These methods operate similarly except for the way that the password is sent across the connection, namely MD5-hashed and clear-text respectively.
If you are at all concerned about password "sniffing" attacks then md5 is preferred. Plain password should always be avoided if possible. However, md5 cannot be used with the db_user_namespace feature. If the connection is protected by SSL encryption then password can be used safely (though SSL certificate authentication might be a better choice if one is depending on using SSL).

After altering this file, don't forget to restart your PostgreSQL server. If you're on Linux, that would be sudo service postgresql restart.

/etc/init.d/postgresql reload

Install Ember-CLI

Getting setup with our tools

Let's start by making sure all relevant dev tools are installed on our machine. I am using the following:

• Ruby 2.1.1
• Rails 4.1.1
• Node 0.10.26
• npm 1.4.7
• Postgres (only necessary because we are deploying to Heroku)

Versions at or above these versions should be OK for following along. Please refer elsewhere on how to install these tools on your development machine.
Next I will install ember-cli

1	npm install -g ember-cli

Confirm that you have ember-cli installed:

1	ember --version

You should see:

1	version: 0.0.27

Or a greater version.

Install and Upgrade node

Install:

apt-get install node


1) Clear NPM's cache:

sudo npm cache clean -f

2) Install a little helper called 'n'

sudo npm install -g n

3) Install latest stable NodeJS version

sudo n stable

Alternatively pick a specific version and install like this:

sudo n 0.8.20

Nginx with Passenger Giving Bad Gateway 502 Error

Recently i have installed and configured nginx with passenger, and
When deployed and configured, Nginx reports a 502 Bad Gateway exception. Digging throught the Nginx error log (in /var/log/nginx), the error becomes clear:

Exception RuntimeError in Rack application object (Missing secret_key_base for 'production' environment, set this value in config/secrets.yml)

Opening secrets.yml shows that there is no value for production:

development:
  secret_key_base: **not_for_prying_eyes**

test:
  secret_key_base: **not_for_prying_eyes**

# Do not keep production secrets in the repository,
# instead read values from the environment.
production:
  secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>

You can either set an environment variable, or directly configure a value here (you can run rake secret to generate a key). Just make sure that if you do the latter, you've added secrets/yml to your .gitignore!