When deploying a Rails app with Capistrano, I want Bundler to install gems to shared/bundles dir ONLY IF it can't find gems installed systemwide already. How do I do it?
For example, if I have a pg gem v 0.14 already installed on the system, I want Bundler to use it and not build and install a new one into shared/bundles dir of my application.
I'm using Ubuntu Server and RVM is installed for multiple users.
Bundler allows using shared(rubygems) and vendored(bundler) gems, by default bundler/capistrano is configured with:
set :bundle_flags, "--deployment --quiet"
which forces vendored gems only,
you can switch back to shared gems with explicit:
set :bundle_flags, "--system --quiet"
to still install in vendor but use shared gems too:
set :bundle_flags, "--path #{shared_path}/bundles --quiet"
if the deployment was already ran with --deployment(the default) then it could help to run the deploy once with:
set :bundle_flags, "--no-deployment"
This is actually a feature of Bundler, essentially it's dependency isolation – you don't want your app depending on an outside, system gems like this. Updating the system gem could then have a impact on running applications.
If you're already using capistrano you should be using require "bundler/capistrano" in your script which will install them in shared/bundles anyway. You could look into packaging before hand as well: http://gembundler.com/v1.2/bundle_package.html
来源：https://stackoverflow.com/questions/14836119/how-to-tell-bundler-to-use-gems-installed-systemwide-production-deployment