doc install: add section about Ubuntu 12.04 Precise Pangolin

doc/source/install.rst

@@ -149,6 +149,34 @@ Install ::
 
 If you want to use `MeCab <http://mecab.sourceforge.net/>`_ as a tokenizer. please install groonga-tokenizer-mecab package.
 
+Install groonga-tokenizer-mecab package::
+
+  % sudo apt-get -y install groonga-tokenizer-mecab
+
+Ubuntu 12.04 Precise Pangolin
+-----------------------------
+
+.. note::
+
+   You need to enable the universe section in Ubuntu's software sources.
+
+.. note::
+
+   You need to enable the security update repository.
+
+/etc/apt/sources.list.d/groonga.list::
+
+  deb http://packages.groonga.org/ubuntu/ precise universe
+  deb-src http://packages.groonga.org/ubuntu/ precise universe
+
+Install ::
+
+  % sudo apt-get update
+  % sudo apt-get -y --allow-unauthenticated install groonga-keyring
+  % sudo apt-get -y install mysql-server-mroonga
+
+If you want to use `MeCab <http://mecab.sourceforge.net/>`_ as a tokenizer. please install groonga-tokenizer-mecab package.
+
 Install groonga-tokenizer-mecab package::
 
   % sudo apt-get -y install groonga-tokenizer-mecab