Add sample recipe in documentation

README.md

@@ -219,6 +219,107 @@ design and usage of Domain Specific Languages in Ruby, and refactor
 all my scripts as "recipes" in a common language.
 
 
+Sample recipe
+-------------
+
+  Based on the previous template example (FreeBSD jails.conf
+template):
+
+    require 'producer/stdlib'
+
+    JAILS_ROOT  = '/var/jails'.freeze
+    ZROOT       = 'tank/jails'.freeze
+    INTERFACE   = 're0'.freeze
+    SETS        = {
+      base: '2b028a894d25711ad496762622a52d74b1e32ee04693ad1cf056e3ddcdc23975',
+      src:  'f919287a5ef51d4f133f27c99c54f2e8054f408d3dd53bc60f4e233cc75ec03d'
+    }.freeze
+    JAILS       = [
+      {
+        name:   'freebsd-10r1',
+        src:    true,
+        addr4:  '10.0.0.1'
+      },
+      {
+        name:   'freebsd-10r1-gcc',
+        src:    true,
+        addr4:  '10.0.0.2'
+      }
+    ].freeze
+
+    task :freebsd_archives_fetch do
+      SETS.keys.each { |set| condition { no_file? "/tmp/#{set}.txz"} }
+
+      SETS.each do |set, sum|
+        sh <<-eoh
+          cd /tmp && \
+          fetch ftp://ftp.freebsd.org:/pub/FreeBSD/releases/amd64/10.1-RELEASE/#{set}.txz && \
+          sha256 -c #{sum} #{set}.txz
+        eoh
+      end
+    end
+
+    task :jails_fs_create do
+      condition { no_sh "zfs list #{ZROOT}" }
+      sh "zfs create -o mountpoint=#{JAILS_ROOT} -o compress=lz4 #{ZROOT}"
+    end
+
+    JAILS.each do |jail|
+      root  = "#{JAILS_ROOT}/#{jail[:name]}"
+      fs    = "#{ZROOT}/#{jail[:name]}"
+
+      task :jail_initialize do
+        condition { no_sh "zfs list #{fs}@install" }
+
+        task :jail_fs_create do
+          condition { no_sh "zfs list #{fs}" }
+
+          sh "zfs create #{fs}"
+
+          SETS.keys.each do |set|
+            next if set == 'src' && !jail[:src]
+            sh "tar -JxC #{root}/ -f /tmp/#{set}.txz"
+          end
+        end
+
+        task :rc_conf do
+          file_write_once "#{root}/etc/rc.conf", <<-eoh
+    hostname=#{jail[:name]}
+    # ...
+          eoh
+        end
+
+        task :root_passwd do
+          sh "chroot #{root} pw user mod root -w random"
+        end
+
+        task :mail_aliases do
+          condition { no_file? "#{root}/etc/mail/aliases.db" }
+
+          sh "chroot #{root} make -C /etc/mail aliases"
+        end
+
+        freebsd_update_patch_interactive "#{root}/usr/sbin/freebsd-update"
+
+        task :jail_snapshot_install do
+           sh "zfs snapshot #{fs}@install"
+        end
+      end
+
+      task :jail_update do
+        condition { no_sh "zfs list #{fs}@update" }
+
+        sh "chroot #{root} freebsd-update fetch install"
+        sh "zfs snapshot #{fs}@update"
+      end
+    end
+
+    task :jails_conf do
+      conf = template 'freebsd/jail.conf', if: INTERFACE, jails: JAILS
+      file_write_once '/etc/jail.conf', conf
+    end
+
+
 Similar or related code and tools
 ---------------------------------