How to Use Gem to Install Rails on Ubuntu

How to use gem to install Rails on Ubuntu

After upgrading to Rails 4.2.4 on Ubuntu 14.04 using RVM I needed to do this:

sudo apt-get install libgmp-dev


sudo apt-get install libgmp3-dev

Full stacktrace:

How do I use gems with Ubuntu?

Where are my Gems?

You can find where your gems are stored using the gem environment command. For example:

chris@chris-laptop:~$ gem environment
RubyGems Environment:

- RUBY VERSION: 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]
- INSTALLATION DIRECTORY: /usr/lib/ruby/gems/1.8
- RUBY EXECUTABLE: /usr/bin/ruby1.8
- ruby
- x86-linux
- /usr/lib/ruby/gems/1.8
- /home/chris/.gem/ruby/1.8
- :update_sources => true
- :verbose => true
- :benchmark => false
- :backtrace => false
- :bulk_threshold => 1000

If you look at the "GEM PATHS:" section you can see that gems can be stored in two places on my laptop: /usr/lib/ruby/gems/1.8 or in the .gem directory in my home dir.

You can also see that executables are stored in EXECUTABLE DIRECTORY which in this case is /usr/bin.

Because /usr/bin is in my path this lets me run cap, merb, rails etc.

Updating your PATH

If for some reason your EXECUTABLE DIRECTORY isn't on your path (for example if it is /var/lib/gems/1.8/bin) then you need to update your PATH variable.

Assuming that you are using the bash shell. You can do this quickly for the current session by typing the following at the shell prompt; let's pretend that you want to add /var/lib/gems/1.8/bin to the path:

export PATH=$PATH:/var/lib/gems/1.8/bin

and press return. That appends the new directory to the end of the current path. Note the colon between $PATH and /var/lib/gems/1.8/bin

To set the value for all sessions you will need to edit either your .profile or .bashrc file and add the same line to the end of the file. I usually edit my .bashrc file for no reason other than that's what I've always done. When finished, save the file and then refresh your environment by typing:


at the shell prompt. That will cause the .bashrc to get reread.

At any point you can check the current value of $PATH by typing

echo $PATH

at the shell prompt.

Here's a sample from one of my own servers, where my username is "chris" and the machine name is "chris-laptop":

chris@chris-laptop:~$ echo $PATH
chris@chris-laptop:~$ export PATH=$PATH:/var/lib/gems/1.8/bin
chris@chris-laptop:~$ echo $PATH

My Gem won't load!

"Ruby gems won't load even though installed" highlights a common problem using multiple different versions of Ruby; Sometimes the Gem environment and Gem path get out of sync:

rb(main):003:0> Gem.path

=> ["/opt/ruby1.9/lib/ruby1.9/gems/1.9.1"]
irb(main):004:0> exit

Any Ruby process here is looking only in one place for its Gems.

:~/$ gem env
RubyGems Environment:
- RUBY VERSION: 1.9.1 (2009-05-12 patchlevel 129) [x86_64-linux]
- INSTALLATION DIRECTORY: /opt/ruby1.9/lib/ruby/gems/1.9.1
- RUBY EXECUTABLE: /opt/ruby1.9/bin/ruby1.9
- EXECUTABLE DIRECTORY: /opt/ruby1.9/bin
- ruby
- x86_64-linux
- /opt/ruby1.9/lib/ruby/gems/1.9.1
- /home/mark/.gem/ruby/1.9.1
- :update_sources => true
- :verbose => true
- :benchmark => false
- :backtrace => false
- :bulk_threshold => 1000

Look carefully at the output of gem environment:

- /opt/ruby1.9/lib/ruby/gems/1.9.1

This isn't the same path as returned by Gem.path:


It's hard to say what exactly caused lib/ruby to change to lib/ruby1.9 but most likely the developer was working with multiple Ruby versions. A quick mv or ln will solve the problem.

If you do need to work with multiple Ruby versions then you really should be using rvm.

Can I install gems with apt-get on Ubuntu?

First, download *.tar file, unpack this file, then go to rubygems directory in your console, and type

ruby setup.rb

That's it :)

Ruby: How to install a specific version of a ruby gem?

Use the -v flag:

$ gem install fog -v 1.8

Error when run gem install rails

Thanks to all for your help.

At last this problem is solved, when I update my computer using Ubuntu Update Manager.

I don't know why solved the problem after updates. But I am sure it is solved by Updating all.

Specially thanks to majioa.

Problems installing rails in Ubuntu

Here are the steps that I took to install rbenv in ubuntu server

git clone ~/.rbenv
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
source ~/.bashrc
git clone ~/.rbenv/plugins/ruby-build
rbenv -v
rbenv install 2.5.3
rbenv global 2.5.3
rbenv rehash
ruby -v
gem install bundler
# inside rails application
bundle install


  • Line 1: clone rbenv project
  • line 2-4: enter rbenv path and settings to your bashrc
  • rbenv -v = check whether your rbenv is running correctly
  • then install ruby version (I checked above you running version 2.5.3)
  • rbenv global 2.5.3 (set version 2.5.3 in any folder paths)
  • rbenv rehash (after you set global / local make sure you do rehash)

Can't gem install rails

Turns out I needed to do this:

sudo apt-get install ruby-dev build-essential

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