Bits, bytes & errors

[pramodtech]

Install Vim Railscasts theme

Link for railscasts theme https://github.com/jpo/vim-railscasts-theme

Install this file as ~/.vim/colors/railscasts.vim 

put "colorscheme railscasts" in your .gvimrc 

f you are using Ubuntu, you can get the benefit of this theme in your  gnome-terminals by taking the following steps:  1: sudo apt-get install ncurses-term  2: put the following in your .vimrc      

 if $COLORTERM == 'gnome-terminal'          set term=gnome-256color          colorscheme railscasts      else          colorscheme default      endif 

[pramodtech]

Display current Git branch in bash prompt

Edit .bashrc file.

vim ~/.bashrc

At the end of file enter the following piece of code:

function parse_git_branch () { git branch 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/ (\1)/' }   RED="\[\033[0;31m\]" YELLOW="\[\033[0;33m\]" GREEN="\[\033[0;32m\]" NO_COLOR="\[\033[0m\]"   PS1="$GREEN\u@\h$NO_COLOR:\w$YELLOW\$(parse_git_branch)$NO_COLOR\$ "

[pramodtech]

Amazon EC2 - RVM/Bundle install Cannot allocate memory

If instance type is t1.micro, you will probably get below error.

Cannot allocate memory - /home/ubuntu/.rvm/rubies/ruby-2.0.0-p353/bin/ruby extconf.rb

Solution: Upgrade instance type.(It comes with additional cost)

How: 

Using AWS Management Console:

Right-Click on the instance

Instance Lifecycle > Stop

Wait...

Instance Management > Change Instance Type

[pramodtech]

Ubuntu: Find a port being used by process and kill it

sudo netstat -lpn |grep :4000

tcp       0 0.0.0.0:4000           LISTEN      17469/ruby

kill -9 17469

[pramodtech]

Linux / Unix Command: curl

curl - transfer a URL

curl [options] [URL...]

curl is a client to get documents/files from or send documents to a server, using any of the supported protocols (HTTP, HTTPS, FTP, GOPHER, DICT, TELNET, LDAP or FILE). The command is designed to work without user interaction or any kind of interactivity.

curl offers a busload of useful tricks like proxy support, user authentication, ftp upload, HTTP post, SSL (https:) connections, cookies, file transfer resume and more.

15 Practical Linux cURL Command Examples.

[pramodtech]

JMeter Load Testing Beginner Tutorial

[pramodtech]

Using DIV instead of Table in html

Just keep adding divs to meet your needs. If you want divs to act as columns, float them and set their width. 

Why not use tables for layout in HTML?

Example: 

<div id="wrapper" style="width: 1000px;margin: auto;"> <div id="header" style="border: 1px solid black">Header</div> <div id="nav" style="border: 1px solid black">Navigation</div> <div id="content"> <div id="col1" style="float:left;width:98px;border: 1px solid black">Column 1</div> <div id="col2" style="float:left;width:148px;border: 1px solid black">Column 2</div> <div id="col3" style="float:left;width:598px;border: 1px solid black">Column 3</div> <div id="col4" style="float:left;width:148px;border: 1px solid black">Column 4</div> </div> <div id="row" style="border: 1px solid black;clear: both;">Row</div> <div id="footer" style="border: 1px solid black">Footer</div> </div>

[pramodtech]

How to update Google chrome in Ubuntu?

Update-manager will do the job for you, just install the latest updates.

You can do same using command line 

sudo apt-get update

sudo apt-get upgrade

From the Chrome EULA page:

Note: Installing Google Chrome will add the Google repository so your system will automatically keep Google Chrome up to date. If you don't want Google's repository, do "sudo touch /etc/default/google-chrome" before installing the package.

[pramodtech]

Difference between apt-get update & apt-get-upgrade

apt-get update doesn't actually install new versions of software.

apt-get update downloads the package lists from the repositories and "updates" them to get information on the newest versions of packages and their dependencies. It will do this for all repositories and PPAs. 

apt-get upgrade will fetch new versions of packages existing on the machine if APT knows about these new versions by way of apt-get update.

apt-get dist-upgrade will do the same job which is done by apt-get upgrade, plus it will also intelligently handle the dependencies, so it might remove obsolete packages or add new ones.

Source: http://askubuntu.com/a/222352/166345

[pramodtech]

14 Ways to Welcome 2014 - Sri Sri Ravi Shankar

[pramodtech]

Step by Step - Install RVM, Rails, Passenger and Nginx on Ubuntu 12.04

For installing RVM, Ruby , Rails please follow below link:

http://ryanbigg.com/2010/12/ubuntu-ruby-rvm-rails-and-you/

Once you have installed everything you need for development, let's see how to deploy our web application on Nginx with Passenger.

Adding APT repository

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 561F9B9CAC40B2F7

sudo apt-get install apt-transport-https ca-certificates

Create a file /etc/apt/sources.list.d/passenger.list and insert following lines.

deb https://oss-binaries.phusionpassenger.com/apt/passenger precise main

Secure passenger.list and update your APT cache

sudo chown root: /etc/apt/sources.list.d/passenger.list sudo chmod 600 /etc/apt/sources.list.d/passenger.list sudo apt-get update

Install the packages

sudo apt-get install nginx-extras passenger

Edit /etc/nginx/nginx.conf and uncomment passenger_root and passenger_ruby.

Restart Nginx

sudo service nginx restart

Add a server virtual host entry to your Nginx configuration file. The virtual host’s root must point to your Ruby on Rails application’s public folder. You can find config file at /etc/nginx/sites-enabled. You can either add server entry to default file or create new file.

http { ... server { listen 80; server_name localhost; root /webapps/mycook/public; passenger_enabled on; passenger_ruby /home/username/.rvm/rubies/ruby-2.0.0-p353/bin/ruby; passenger_app_env development; } ... }

Replace server_name with appropriate domain name/public IP.

If your web application using RVM gemset (using .ruby-version) then you need to use that as passenger_ruby. To find which one your web application is using, go to application directory and run below command 

which passenger-config

This will give output something like 

/opt/passenger/bin/passenger-config or /usr/bin/passenger-config

Now add --ruby-command to it and run 

/opt/passenger/bin/passenger-config --ruby-command

Result:

passenger-config was invoked through the following Ruby interpreter: Command: /usr/local/rvm/wrappers/ruby-1.9.3-p392/ruby Version: ruby 1.9.3p392 (2013-02-22 revision 39386) [x86_64-darwin12.2.1] To use in Apache: PassengerRuby /usr/local/rvm/wrappers/ruby-1.9.3-p392/ruby To use in Nginx : passenger_ruby /usr/local/rvm/wrappers/ruby-1.9.3-p392/ruby To use with Standalone: /usr/local/rvm/wrappers/ruby-1.9.3-p392/ruby /opt/passenger/bin/passenger start

Use the respective path given in above.

Reference:

http://www.modrails.com/documentation/Users%20guide%20Nginx.html

[pramodtech]

Net::SMTPAuthenticationError 534-5.7.14 while sending emails using Gmail

Possible reasons:

Username/password is wrong.

Your gmail account is blocked for security reasons.

Solution to #2

Go to http://www.google.com/accounts/DisplayUnlockCaptcha and click continue

[pramodtech]

Rails - ActiveRecord select specific columns

Use pluck as a shortcut to select one or more attributes without loading a bunch of records just to grab the attributes you want.

Person.pluck(:name)

instead of

Person.all.map(&:name)

Pluck returns an Array of attribute values type-casted to match the plucked column names, if they can be deduced. Plucking an SQL fragment returns String values by default.

Person.pluck(:id) # SELECT people.id FROM people # => [1, 2, 3] Person.pluck(:id, :name) # SELECT people.id, people.name FROM people # => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']] Person.pluck('DISTINCT role') # SELECT DISTINCT role FROM people # => ['admin', 'member', 'guest'] Person.where(age: 21).limit(5).pluck(:id) # SELECT people.id FROM people WHERE people.age = 21 LIMIT 5 # => [2, 3] Person.pluck('DATEDIFF(updated_at, created_at)') # SELECT DATEDIFF(updated_at, created_at) FROM people # => ['0', '27761', '173']

[pramodtech]

25 posts!

[pramodtech]

Rails new app not starting: ExecJS and could not find a JavaScript runtime

Installing a javascript runtime library on Ubuntu such as nodejs solves this problem.

To install nodejs, you can type the following command in the terminal.

sudo apt-get install nodejs

[pramodtech]

[pramodtech]

Install ruby gems locally

I got below error while installing gem on my test server (Ubuntu machine), while my application worked fine on my dev machine.

Unable to download data from http://rubygems.org/ - Errno::ECONNREFUSED: Connection refused - connect(2)

Solution:

Install gem from local repo. How to do that?

On your local machine run below command

              bundle package

This command will create folder in your app under vendor/cache, this folder will have all required gems for your app.

Now, copy this folder to your test server.

Run below command to install gems

             bundle install - - local

Job done!