How to set up ruby gems on Debian Etch as non-root

This tutorial describes how to install Ruby gems to your home directory. The gems you install there will not be visible to other user, and they won't affect the system default configuration. You'll need root access in the first few steps to install Ruby and the rubygems packaging framework itself. It is possible to install those without root access as well, but that's beyond the scope of this tutorial.

You need a working ruby and rubygems. You have to install it as root:
$ su -
# apt-get update
# apt-get install ruby1.8 rubygems
(if you want to install gems which need C compilation, e.g. ruby-sqlite:)
# apt-get install ruby1.8-dev gcc libc6-dev
# ruby -v
ruby 1.8.5 (2006-08-25) [i486-linux]

This is optional, to have the latest rubygems (you can do this any time later):
$ su -
# gem install rubygems-update
# /var/lib/gems/1.8/bin/update_rubygems
# rm -f /usr/bin/gem
# ln -s gem1.8 /usr/bin/gem
$ gem -v

All the rest works as non-root:
$ export GEM_HOME=$HOME/gems
$ rm -rf $GEM_HOME
$ mkdir $GEM_HOME{,/cache,/doc,/gems,/specifications}
$ cp -a /var/lib/gems/1.8/cache/sources-*.gem $GEM_HOME/cache/
$ cp -a /var/lib/gems/1.8/gems/sources-* $GEM_HOME/gems/
$ cp -a /var/lib/gems/1.8/specifications/sources-*.gemspec $GEM_HOME/specifications/
$ gem update
Updating installed gems...
Bulk updating Gem source index for: http://gems.rubyforge.org
(this takes a few minutes)
Gems: [] updated

Try querying or installing something:
$ gem search rake --remote
$ gem install rake
Successfully installed rake-0.8.4
Installing ri documentation for rake-0.8.4...
Installing RDoc documentation for rake-0.8.4...

Try installing rails:
$ gem install rails --include-dependencies
(... takes some time)
$ ~/gems/bin/rails -v

Try installing something which needs C code. Please note that you have to install the C prerequisite (libsqlite3) as root:
$ su -c 'apt-get install libsqlite3-dev'
$ gem search sqlite3 --remote
$ gem install --platform ruby sqlite3-ruby
Building native extensions. This could take a while...
Successfully installed sqlite3-ruby-1.2.4
1 gem installed
Installing ri documentation for sqlite3-ruby-1.2.4...
Installing RDoc documentation for sqlite3-ruby-1.2.4...

Please note that you need the GEM_HOME environment variable set for installing gems and for running applications requiring gems. To have this variable set for you, do this:
$ echo 'export GEM_HOME=$HOME/gems' >>~/.bashrc
$ echo 'export GEM_HOME=$HOME/gems' >>~/.bash_profile

If you need the rails command without having to specify ~/gems/bin/rails, make sure you have an export PATH=$HOME/gems/bin:$PATH in your .bashrc and/or .bash_profile.

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