How to Use Gems With Ubuntu

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:
- RUBYGEMS VERSION: 1.3.2

- 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
- EXECUTABLE DIRECTORY: /usr/bin
- RUBYGEMS PLATFORMS:
- ruby
- x86-linux
- GEM PATHS:
- /usr/lib/ruby/gems/1.8
- /home/chris/.gem/ruby/1.8
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :benchmark => false
- :backtrace => false
- :bulk_threshold => 1000
- REMOTE SOURCES:

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:

bash

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

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:
- RUBYGEMS VERSION: 1.3.7
- 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
- RUBYGEMS PLATFORMS:
- ruby
- x86_64-linux
- GEM PATHS:
- /opt/ruby1.9/lib/ruby/gems/1.9.1
- /home/mark/.gem/ruby/1.9.1
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :benchmark => false
- :backtrace => false
- :bulk_threshold => 1000
- REMOTE SOURCES:
- http://rubygems.org/

Look carefully at the output of gem environment:

  - GEM PATHS:
- /opt/ruby1.9/lib/ruby/gems/1.9.1

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

["/opt/ruby1.9/lib/ruby1.9/gems/1.9.1"]

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 :)

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

or

sudo apt-get install libgmp3-dev

Full stacktrace: http://ruby-on-rails-eq8.blogspot.co.uk/2015/10/solving-ubuntu-1404-ruby-c-dependancy.html

Ruby gem permission denied /var/lib/gems using Ubuntu

You need to prefix the gem command with sudo because /var/lib/gems is owned by root. You could also take a look at RVM which allows really easy installation and management of gems and Ruby versions. Best part, it's all in your home dir!

EDIT: per @AndrewMarshall's comment bellow, rbenv is an alternative to RVM.

How do I package a Ruby application for Ubuntu, including its gem dependencies?

Because apt-get and gem are both dependency resolving, you can just make a meta package that depends on ruby1.9.1 (which itself brings in Rubygems and everything else). Then in the post-install script, just do a sudo gem1.9.1 install maid.

I can't lay out the whole process of making a package here, but there are a lot of good tutorials on it around the web.

You don't have write permissions for the /var/lib/gems/2.3.0 directory

You first need to uninstall the ruby installed by Ubuntu with something like sudo apt-get remove ruby.

Then reinstall ruby using rbenv and ruby-build according to their docs:

cd $HOME
sudo apt-get update
sudo apt-get install git-core curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libxml2-dev libxslt1-dev libcurl4-openssl-dev libffi-dev

git clone https://github.com/rbenv/rbenv.git ~/.rbenv
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
exec $SHELL

git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build
echo 'export PATH="$HOME/.rbenv/plugins/ruby-build/bin:$PATH"' >> ~/.bashrc
exec $SHELL

rbenv install 2.3.1
rbenv global 2.3.1
ruby -v

The last step is to install Bundler:

gem install bundler
rbenv rehash

How can I get RubyGems 1.3.6 on Ubuntu 10.4

I got it working using

gem install rubygems-update
cd /var/lib/gems/1.9.1/bin
sudo ./update_rubygems


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