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

I have ruby installed on my ubuntu 16.04.

$which ruby  

/usr/bin/ruby

$ruby -v 

ruby 2.3.0p0 (2015-12-25) [x86_64-linux-gnu]

$gem install bundler 

ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /var/lib/gems/2.3.0 directory.

Solution 1:

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 install curl
curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt-get update
sudo apt-get install git-core zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev software-properties-common libffi-dev nodejs yarn

Now we will install rbenv (recommended, see docs)

cd
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 3.0.1
rbenv global 3.0.1
ruby -v

The last step is to install Bundler:

gem install bundler
rbenv rehash

Then enjoy!

Derek

Update: This answer has been updated and tested successfully on Ubuntu 20.04.

Solution 2:

If you want to use the distribution Ruby instead of rb-env/rvm, you can set up a GEM_HOME for your current user. Start by creating a directory to store the Ruby gems for your user:

$ mkdir ~/.ruby

Then update your shell to use that directory for GEM_HOME and to update your PATH variable to include the Ruby gem bin directory.

$ echo 'export GEM_HOME=~/.ruby/' >> ~/.bashrc
$ echo 'export PATH="$PATH:~/.ruby/bin"' >> ~/.bashrc
$ source ~/.bashrc

(That last line will reload the environment variables in your current shell.)

Now you should be able to install Ruby gems under your user using the gem command. I was able to get this working with Ruby 2.5.1 under Ubuntu 18.04. If you are using a shell that is not Bash, then you will need to edit the startup script for that shell instead of bashrc.

Solution 3:

(January 2019) To install Ruby using the Rbenv script, follow these steps:

1. First, update the packages index and install the packages required for the ruby-build tool to build Ruby from source:

sudo apt-get remove ruby
sudo apt update
sudo apt install git curl libssl-dev libreadline-dev zlib1g-dev autoconf bison build-essential libyaml-dev libreadline-dev libncurses5-dev libffi-dev libgdbm-dev

2. Next, run the following curl command to install both rbenv and ruby-build:

curl -sL https://github.com/rbenv/rbenv-installer/raw/main/bin/rbenv-installer | bash -

3. Add $HOME/.rbenv/bin to the system PATH.

If you are using Bash, run:

echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
source ~/.bashrc

If you are using Zsh run:

echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.zshrc
echo 'eval "$(rbenv init -)"' >> ~/.zshrc
source ~/.zshrc

4. Install the latest stable version of Ruby and set it as a default version with:

rbenv install 2.5.1
rbenv global 2.5.1

To list all available Ruby versions you can use: rbenv install -l

5. Verify that Ruby was properly installed by printing out the version number:

ruby -v

# Output
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]

SOURCE: How To Install Ruby on Ubuntu 18.04

EDIT: Install rubygems:

sudo apt-get install rubygems