babysnakes · June 10, 2012 05:11 · Jun 10, 2012 · Jun 10, 2012 · Jun 10, 2012
diff --git a/README.md b/README.md
@@ -85,6 +85,11 @@ options are the ones I was interested in. See the source of the
 configuration options.
 
 ```ruby
+require 'chef'
+require 'chef/knife'
+require 'chef/knife/bootstrap'
+require "chef/knife/core/bootstrap_context"
+
 # Using knife's facilities to generate the ssh command to bootstrap our
 # machines. We don't use knife directly because it doesn't report bad
 # exit code from the remote ssh commands.
@@ -114,6 +119,9 @@ command. It's also returns the output. Later we'll see how to use it.
 (This function is copied from code I found in [StackOverflow][so]).
 
 ```ruby
+# don't forget to require 'net/ssh'!
+
+
 # A utility method that helps getting output code from ssh remote
 # command. Idea taken from stackoverflow.com.
 #

diff --git a/README.md b/README.md
@@ -2,7 +2,7 @@
 
 Here is a description of the steps I took to cause `knife bootstrap`
 to exit with error when the remote bootstrap process fails. I was
-already calling the bootstrap programmatic (because I was adding a lot
+already calling the bootstrap programmatically (because I was adding a lot
 of business logic to it) so I didn't patch the bootstrap class but
 pulled out the pieces I needed.
 

diff --git a/README.md b/README.md
@@ -0,0 +1,197 @@
+## Modifying _'knife bootstrap'_ to exit with error upon failure.
+
+Here is a description of the steps I took to cause `knife bootstrap`
+to exit with error when the remote bootstrap process fails. I was
+already calling the bootstrap programmatic (because I was adding a lot
+of business logic to it) so I didn't patch the bootstrap class but
+pulled out the pieces I needed.
+
+### The template.
+
+Chef uses an ERB template to construct the bootstrap remote
+command. We need to add `set -e` to this script for it to exit with
+error whenever a command is exited with non-zero exit code. Another
+option would be to connect the various commands with `&&`. The main
+idea is to stop the execution of the script upon command failure (at
+least the commands you care about). Otherwise you'll always get the
+output of the last command even if all the previous commands failed to
+execute.
+
+Here's my modifications to the default (in 0.10.8) template (you can
+compare it to the one included in the gem):
+
+```bash
+bash -c '
+(
+set -e
+
+<%= "export http_proxy=\"#{knife_config[:bootstrap_proxy]}\"" if knife_config[:bootstrap_proxy] -%>
+
+if [ ! -f /usr/bin/chef-client ]; then
+  apt-get update || true
+  apt-get install -y ruby ruby1.8-dev build-essential wget libruby-extras libruby1.8-extras
+  cd /tmp
+  wget <%= "--proxy=on " if knife_config[:bootstrap_proxy] %>http://production.cf.rubygems.org/rubygems/rubygems-1.6.2.tgz
+  tar zxf rubygems-1.6.2.tgz
+  cd rubygems-1.6.2
+  ruby setup.rb --no-format-executable
+fi
+
+gem update --no-rdoc --no-ri
+gem install ohai --no-rdoc --no-ri --verbose
+gem install chef --no-rdoc --no-ri --verbose <%= bootstrap_version_string %>
+
+mkdir -p /etc/chef
+
+(
+cat <<'EOP'
+<%= validation_key %>
+EOP
+) > /tmp/validation.pem
+awk NF /tmp/validation.pem > /etc/chef/validation.pem
+rm /tmp/validation.pem
+
+<% if @chef_config[:encrypted_data_bag_secret] -%>
+(
+cat <<'EOP'
+<%= encrypted_data_bag_secret %>
+EOP
+) > /tmp/encrypted_data_bag_secret
+awk NF /tmp/encrypted_data_bag_secret > /etc/chef/encrypted_data_bag_secret
+rm /tmp/encrypted_data_bag_secret
+<% end -%>
+
+(
+cat <<'EOP'
+<%= config_content %>
+EOP
+) > /etc/chef/client.rb
+
+(
+cat <<'EOP'
+<%= { "run_list" => @run_list }.to_json %>
+EOP
+) > /etc/chef/first-boot.json
+
+<%= start_chef %>
+)'
+```
+
+### Rendering the template
+
+I use the `Chef::Knife::Bootstrap` class to render the template. The
+options are the ones I was interested in. See the source of the
+`Chef::Knife::Bootstrap` class to get a list of all available
+configuration options.
+
+```ruby
+# Using knife's facilities to generate the ssh command to bootstrap our
+# machines. We don't use knife directly because it doesn't report bad
+# exit code from the remote ssh commands.
+#
+# params:
+# * name    - The name to register in chef as
+# * options - A Hash of options. Accepts the following options:
+#           - :run_list       => The run list.
+#           - :env            => Chef environment to use.
+#           - :template_file  => Knife bootstrap template file to use.
+def generate_ssh_bootstrap_command(name, options)
+  kb = Chef::Knife::Bootstrap.new
+  Chef::Config[:environment] = options[:env]
+  kb.config[:run_list]       = options[:run_list]
+  kb.config[:use_sudo]       = true
+  kb.config[:template_file]  = options[:template_file]
+  kb.config[:chef_node_name] = name
+  kb.ssh_command
+end
+```
+
+### Getting the exit code of remote ssh command
+
+The function below returns the exit code of the remote ssh
+command. It's also returns the output. Later we'll see how to use it.
+
+(This function is copied from code I found in [StackOverflow][so]).
+
+```ruby
+# A utility method that helps getting output code from ssh remote
+# command. Idea taken from stackoverflow.com.
+#
+# params:
+# * ssh     - Net::SSH object to use (see example below)
+# * command - The command (string) to execute.
+#
+# You can optionally add a block that accepts data. The data is both stderr
+# and stdout, so you can add a block with 'print data' to see on the console
+# both stdout and error.
+#
+# The stdout and stderr are combined because some commands output
+# to stderror (like wget).
+#
+# Returns: data(stdout and err combined), exit_code, exit_signal(what is this?)
+#
+# Sample usage:
+#
+#     Net::SSH.start(server, Etc.getlogin) do |ssh|
+#       puts ssh_exec!(ssh, "true").inspect
+#       # => ["", "", 0, nil]
+#       puts ssh_exec!(ssh, "false").inspect  
+#       # => ["", "", 1, nil]
+#     end
+def ssh_exec!(ssh, command)
+  output_data = ""
+  exit_code = nil
+  exit_signal = nil
+  ssh.open_channel do |channel|
+    channel.exec(command) do |ch, success|
+      unless success
+        abort "FAILED: couldn't execute command (ssh.channel.exec)"
+      end
+      channel.on_data do |ch,data|
+        output_data+=data
+        if block_given?
+          yield data
+        end
+      end
+
+      channel.on_extended_data do |ch,type,data|
+        output_data+=data
+        if block_given?
+          yield data
+        end
+      end
+
+      channel.on_request("exit-status") do |ch,data|
+        exit_code = data.read_long
+      end
+
+      channel.on_request("exit-signal") do |ch, data|
+        exit_signal = data.read_long
+      end
+    end
+  end
+  ssh.loop
+  [output_data, exit_code, exit_signal]
+end
+```
+
+### Sample Usage of the _ssh_exec!_ command
+
+Here is how I call the above function. Notice I supply a block that
+prints the output of the commands without newlines (`say` is a utility
+method in Thor).
+
+```ruby
+Net::SSH.start(hostname, user) do |ssh|
+  output, exit_code, signal =  ssh_exec!(ssh, command) do |data|
+    say(data, {}, false)
+  end
+  if exit_code != 0
+    error = "Bootstrap script exited with exit code: #{exit_code}"
+    log.error("output of failed bootstrap command:\n#{output}")
+    raise error
+  end
+end
+```
+
+[so]: http://stackoverflow.com/questions/3386233/how-to-get-exit-status-with-rubys-netssh-library
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