[chef] Outdated Documentation

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Hi guys,

Trying to use chef tools to build desired docker container.
I'm following the article : 
http://docs.opscode.com/containers.html
And my installation attempt of knife-container gem fails with this error:
ERROR:  Could not find a valid gem 'knife-container' (>= 0) in any repository
ERROR:  Possible alternatives: chef-container, zip-container, knife-softlayer,
henry-container, knife-config

Is it actually normal and i'm missing something?
Or this actullay is outdated documentation?

Regards