vagrant set ip address in loop with maths - ruby

Question

I am trying to write a script to set up a dynamic number of nodes in vagrant.
so it runs as
# -*- mode: ruby -*-
# vi: set ft=ruby :
Vagrant.configure("2") do |config|
$num_instances = 3
(1..$num_instances).each do |i|
$ip = "10.1.10.#{i}+80"
config.vm.define "node#{i}" do |node|
node.vm.box = "generic/ubuntu1604"
node.vm.provider :libvirt do |domain|
domain.memory = 1024
domain.cpus = 1
domain.nic_model_type = "virtio"
domain.kvm_hidden = true
end
node.vm.hostname = "t2-node#{i}"
node.vm.network "public_network",
:ip => $ip,
:type => "bridge" ,
:dev => "br1",
:mode => "bridge",
:use_dhcp_assigned_default_route => true
end
end
end
but I get an error:
Unknown interface eth1
Error: ??? prefix is expected rather than "10.1.10.3+80/255.255.255.0".
so I guess the addition for the $1p variable isn't being done properly?
any ideas?

Answer 1

This is more a ruby question than a vagrant question but you do your string interpolation wrong so the statement
$ip = "10.1.10.#{i}+80"
returns a string that is 10.1.10.3+80 and of course this is not a valid IP.
what you're looking at is
ip = "10.1.10.#{i+80}"
which will make the right math.
You can easily check in irb on your command line
irb(main):001:0> num_instances = 3
=> 3
irb(main):002:0> (1..num_instances).each do |i|
irb(main):003:1* ip = "10.1.10.#{i+80}"
irb(main):004:1> p ip
irb(main):005:1> end
"10.1.10.81"
"10.1.10.82"
"10.1.10.83"
=> 1..3
PS: Note, you dont need all the $ when you declare variables in ruby.