vagrant/website/docs/source/v2/vagrantfile/tips.html.md

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Tips & Tricks - Vagrantfile	vagrantfile-tips

Tips & Tricks

The Vagrantfile is a very flexible configuration format. Since it is just Ruby, there is a lot you can do with it. However, in that same vein, since it is Ruby, there are a lot of ways you can shoot yourself in the foot. When using some of the tips and tricks on this page, please take care to use them correctly.

Loop Over VM Definitions

If you want to apply a slightly different configuration to many multi-machine machines, you can use a loop to do this. For example, if you wanted to create three machines:

(1..3).each do |i|
  config.vm.define "node-#{i}" do |node|
    node.vm.provision "shell",
      inline: "echo hello from node #{i}"
  end
end

Warning: The inner portion of multi-machine definitions and provider overrides are lazy-loaded. This can cause issues if you change the value of a variable used within the configs. For example, the loop below does not work:

# THIS DOES NOT WORK!
for i in 1..3 do
  config.vm.define "node-#{i}" do |node|
    node.vm.provision "shell",
      inline: "echo hello from node #{i}"
  end
end

The "for i in ..." construct in Ruby actually modifies the value of i for each iteration, rather than making a copy. Therefore, when you run this, every node will actually provision with the same text.

This is an easy mistake to make, and Vagrant can't really protect against it, so the best we can do is mention it here.