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According to the Unicorn docs, there are different binaries for Rails apps and other Rack apps:

non-Rails Rack applications

In APP_ROOT, run:


for Rails applications (should work for all 1.2 or later versions)



They seem to also take the same command-line parameters. But Rails is built on top of rack, so I don't understand why this dichotomy is required. Is there any reason you can't just use unicorn for Rails apps?

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up vote 1 down vote accepted

From the unicorn docs,

It is designed to help Rails 1.x and 2.y users transition to Rack, but it is NOT needed for Rails 3 applications. Rails 3 users are encouraged to use unicorn(1) instead of unicorn_rails(1). Users of Rails 1.x/2.y may also use unicorn(1) instead of unicorn_rails(1).

So, no, you don't need to use it at all.

It's worth pointing out that Rails only made the transition to Rack in late version 2 (I forget). So, when Unicorn first got released there were probably still a bunch of apps that had to be supported.

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