Issue:

I followed jakyll installation tutorial starting from ruby installation on Ubuntu 16.04:

# apt install ruby

But after that it’s not possible to istall gems without root permissions:

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

Solution:

Remove ruby with the package manager:

# apt-get remove ruby

Install required dependencies:

# apt-get update
# apt-get install git-core curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev python-software-properties libffi-dev

Install rbenv:

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

Install ruby-build plugin for rbenv:

$ 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

Install latest ruby and set it as default:

$ rbenv install 2.4.2
$ rbenv global 2.4.2

Verify installation:

$ ruby -v
ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-linux]

Install jakyll with non-root permissions:

$ gem install jekyll