Is it safe to change the IP address and domain name of an Chef Node

chef

I have a Chef Node that I'm initially setting up on one network that I need to (physically) move to another network. When this happens, I want the IP address and domain name to change, and the Node name and simple hostname to stay the same.

I know I can do this by deleting the Chef Node and recreating it. Could I also do it by editing Node attributes? Or would that break the client keys or (worse still) the server?

(I'm using Chef 10.16.2 …)

Best Answer

Recreating the node (and client) with the new name is one option, but you can preserve the ones you already have. This requires client configuration - by the time the node retrieves attributes from the Chef server, it's already decided what its name is.

By default, chef-client will set the node name to the fully-qualified domain name of the host, as returned by ohai. You can check what name will be used by invoking ohai directly:

zts@chef ~ % ohai fqdn
[
  "chef.nat0.cryptocracy.com"
]

If that changes when you move the host, you'll need to edit /etc/chef/client.rb to set the desired nodename:

node_name "mynode.example.com"

Take a look at Chef Docs - client.rb for more about this configuration file.

Related Solutions

Why does chef list the node name as “localhost”

The reason seems to be that ohai is running hostname --fqdn, which does give "localhost".

The root cause of the problem seems to be that I set the hostname as "mynodename" instead of "mynodename.example.com". If I do:

sudo hostname mynodename.example.com

Then it does the right thing when I do: hostname --fqdn

Chef recipe read attributes from another node

I assume you've set up roles for web server, database server, etc.

Something like this in the app server recipe:

dbservers = Array.new

search(:node, "role:database_server") do |n|
  n["network"]["interfaces"]["eth0"]["addresses"].each_pair do |address,value|
    dbservers << address if value.has_key?("broadcast")
  end if n["network"]["interfaces"]["eth1"]
end

template "/path/to/app/config/appserver.conf" do
  source 'appserver.conf.erb'
  owner 'foo'
  group 'bar'
  mode 0644
  variables :dbservers => dbservers
end

Then your template will have something like:

<% @dbservers.each do |s| -%>
  connect_to_mysql_at_ip <%= s %>
<% end -%>

There might be a nicer way to get the IP address with Chef 0.10. I think the above code may have Chef 0.9 legacy in it, but it does work.

Best Answer

Related Solutions

Why does chef list the node name as “localhost”

Chef recipe read attributes from another node

Related Topic