opensoul.org:

Obscure RubyGems Error

A week or so ago my gem command magically stopped working. Honestly, it was magic! There is no other logical explanation. The fetcher’s socket marshaled all over, spewing this error:

$ gem --version
1.1.0
$ sudo gem update --system
Updating RubyGems
ERROR:  While executing gem ... (Gem::RemoteFetcher::FetchError)
    Hostname not known: gems.rubyforge.org (SocketError)
    getting size of http://gems.rubyforge.org/Marshal.4.8

Googling different parts of that error didn’t yield anything useful. Lo, I post my solution in case some other poor soul has the same problem. Upgrade to 1.2.0.

Since gem upgrade --system is broken, download the rubygems-update manually.

$ sudo gem install ~/path/to/rubygems-update-1.2.0.gem
$ sudo update_rubygems

Ah, all better. Oh, by the way, rubygems 1.2 rocks!