Knife bootstrap custom client.rb config

rfc071-knife-bootstrap-client-config.md

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+---
+RFC: 71
+Authors: Jay Mundrawala <jdm@chef.io>, Bryan McLellan <btm@chef.io>
+Status: Accepted
+Type: Standards Track
+---
+
+# Knife Bootstrap `client.rb` Configuration
+
+Knife bootstrap currently only allows a select few `client.rb` parameters
+to be specified during bootstrap. This RFC proposes a solution to allow users
+to pass bulk configuration data to `knife bootstrap` to be placed in the
+`client.rb` before the first chef-client run.
+
+## Background
+
+The `knife bootstrap` command supports a small subset of possible parameters
+a user can configure in the `client.rb`. The chef-client cookbook provides a
+template that supports many more, allowing the user to configure additional
+options during a Chef client converge. If something you are trying to do does
+not fit into the template provided, you are also free to specify config files
+in a `client.d` folder that will automatically be loaded. However, because
+the chef-client cookbook is run along with the rest of the run list on the
+first run, your settings do not take effect until the second chef-client
+run.
+
+## Motivation
+
+    As a Chef user,
+    I want to be able to configure chef-client with options that aren't supported by knife bootstrap,
+    so that I do not have to maintain a fork of the bootstrap template,
+    or so that I do not have to learn about bootstrap templates at all,
+    or so that I don't have to make two chef-client runs on bootstrap to apply and use my configuration file.
+
+    As a Chef developer,
+    I want the user to have a generic way to pass custom client configuration file,
+    so that I don't have the maintenance cost of additional bootstrap arguments for new features
+
+## Specification
+
+### Append Config Files From `client.d`
+
+The `chef-client` cookbook adds a block to load all `.rb` files in
+the `client.d` folder. The proposal here is to do the same thing.
+Knife bootstrap will take a `client.d` folder, by default looking
+the chef repo under `bootstrap`, optionally overwritable with a
+`knife.rb` configuration parameter `client_d_path`. The files
+will be loaded in alphabetical order. Knife will still sync all files
+under `client.d`, however only top-level files will the automatically
+loaded. The block to do this would look something like:
+
+```ruby
+Dir.glob("/etc/chef/client.d/*.rb").sort.each do |conf|
+  Chef::Config.from_file(conf)
+end
+```
+
+#### Example
+
+For this example, consider we want to configure Ohai's hostname plugin.
+The execution of this plugin will determine the node name that will be
+assigned to the node we are bootstraping, so it needs to be correct on
+the first run.
+
+We store the `ohai_config.rb` file in the Chef repo on our workstation:
+
+```ruby
+# chef-repo/bootstrap/client.d/ohai_config.rb
+
+ohai.plugin[:hostname][:fqdn_using] = [ :hostname, :nis, :dns ]
+```
+
+```ruby
+# chef-repo/bootstrap/client.d/ohai_plugins/custom_plugin.rb
+
+# My custom ohai plugin
+```
+
+Next we bootstrap the node:
+
+    knife bootstrap 10.0.0.100 -x chefuser -P oneofus
+
+This generates the following `client.rb` and copies it to the box,
+along with all the contents in our chef repo's `client.d` directory:
+
+```ruby
+# /etc/chef/client.rb
+
+log_level        :info
+log_location     STDOUT
+chef_server_url  "https://api.chef.io/organizations/oneofus"
+ohai.plugin_path = "/etc/chef/client.d/ohai_plugins"
+
+Dir.glob("/etc/chef/client.d/*.rb").sort.each do |conf|
+  Chef::Config.from_file(conf)
+end
+```
+
+```ruby
+# /etc/chef/client.d/ohai_config.rb
+
+ohai.plugin[:hostname][:fqdn_using] = [ :hostname, :nis, :dns ]
+```
+
+```ruby
+# /etc/chef/client.d/ohai_plugins/custom_plugin.rb
+
+# My custom ohai plugin
+```
+
+Now, when chef-client runs on the box, our configurations to
+Ohai's hostname plugin will be loaded before Ohai runs, allowing
+the first Chef run to get the correct hostname.
+
+Taking a look under `/etc/chef`, we should see something like:
+
+    [vagrant@localhost ~]$ tree /etc/chef/
+    /etc/chef/
+    ├── client.d
+    │   ├── ohai_config.rb
+    │   └── ohai_plugins
+    │       └── custom_plugin.rb
+    ├── client.pem
+    ├── client.rb
+    ├── first-boot.json
+    ├── trusted_certs
+    │   └── localhost.crt
+    └── validation.pem
+
+## Copyright
+
+This work is in the public domain. In jurisdictions that do not allow for this,
+this work is available under CC0. To the extent possible under law, the person
+who associated CC0 with this work has waived all copyright and related or
+neighboring rights to this work.
+