Chef::Daemon

A class for daemonizing and associated tasks, including:
Changing UID
Changing GID
Managing PID files

Author: AJ Christensen

chef/lib/chef/daemon.rb

@@ -0,0 +1,142 @@
+#
+# Author:: AJ Christensen (<aj@junglist.gen.nz>)
+# Copyright:: Copyright (c) 2008 OpsCode, Inc.
+# License:: Apache License, Version 2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#     http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# I love you Merb (lib/merb-core/server.rb)
+
+require 'chef/config'
+require 'etc'
+
+class Chef
+  class Daemon
+    class << self
+      attr_accessor :name
+=begin
+def daemonize(name)
+  exit if fork
+  Process.setsid
+  exit if fork
+  $stdin.reopen("/dev/null")
+  $stdout.reopen("/tmp/log", "a")
+  $stderr.reopen($stdout)
+end
+=end
+
+      def daemonize(name)
+        @name = name
+        pid = pid_from_file
+        unless running?
+          remove_pid_file()
+          Chef::Log.info("Daemonizing..")
+          begin
+            exit if fork
+            Process.setsid
+            exit if fork
+            Chef::Log.info("Forked, in #{Process.pid}")
+            File.umask 0000
+            $stdin.reopen("/dev/null")
+            $stdout.reopen("/dev/null", "a")
+            $stdout.reopen($stdout)
+            at_exit { remove_pid_file }
+          rescue NotImplementedError => e
+            Chef.fatal!("There is no fork: #{e.message}")
+          end
+        else
+          Chef.fatal!("Chef is already running pid #{pid}")
+        end
+      end
+      
+      def running?
+        if pid_from_file.nil?
+          false
+        else
+          Process.kill(0, pid_from_file)
+          true
+        end
+      rescue Errno::ESRCH, Errno::ENOENT
+        false
+      #rescue Errno::EACCESS => e
+      #  Chef.fatal!("You don't have access to the PID file at #{pid_file}: #{e.message}")
+      end
+    
+      def pid_file
+         Chef::Config[:pid_file] or "/tmp/#{@name}.pid"
+      end
+      
+      def pid_from_file
+        File.read(pid_file).chomp.to_i
+      rescue Errno::ENOENT => e
+        nil
+      end
+    
+      def save_pid_file
+        file = pid_file
+        begin
+          FileUtils.mkdir_p(File.dirname(file))
+        rescue Errno::EACCESS => e
+          Chef.fatal!("Failed store pid in #{File.dirname(file)}, permission denied: #{e.message}")
+        end
+      
+        begin
+          File.open(file, "w") { |f| f.write(Process.pid.to_s) }
+        rescue Errno::EACCESS => e
+          Chef.fatal!("Couldn't write to pidfile #{file}, permission denied: #{e.message}")
+        end
+      end
+    
+      def remove_pid_file
+        FileUtils.rm(pid_file) if File.exists?(pid_file)
+      end
+           
+      def change_privilege
+        if Chef::Config[:user] and Chef::Config[:group]
+          Chef::Log.info("About to change privilege to #{Chef::Config[:user]}:#{Chef::Config[:group]}")
+          _change_privilege(Chef::Config[:user], Chef::Config[:group])
+        elsif Chef::Config[:user]
+          Chef::Log.info("About to change privilege to #{Chef::Config[:user]}")
+          _change_privilege(Chef::Config[:user])
+        end
+      end
+    
+      def _change_privilege(user, group=user)
+        uid, gid = Process.euid, Process.egid
+
+        begin
+          target_uid = Etc.getpwnam(user).uid
+        rescue ArgumentError => e
+          Chef.fatal!("Failed to get UID for user #{user}, does it exist? #{e.message}")
+          return false
+        end
+   
+        begin
+          target_gid = Etc.getgrnam(group).gid
+        rescue ArgumentERror => e
+          Chef.fatal!("Failed to get GID for group #{group}, does it exist? #{e.message}")
+          return false
+        end
+      
+        if (uid != target_uid) or (gid != target_gid)
+          Process.initgroups(user, target_gid)
+          Process::GID.change_privilege(target_gid)
+          Process::UID.change_privilege(target_uid)
+        end
+        true
+      rescue Errno::EPERM => e
+        Chef.fatal!("Permission denied when trying to change #{uid}:#{gid} to #{user}:#{group}. #{e.message}")
+      end
+    end
+  end
+end