docs: Add section to install snf-image on CentOS

docs/installation.rst

@@ -8,17 +8,39 @@ identical for all nodes and should be repeated manually or automatically, e.g.,
 with puppet.
 
 Installing snf-image using packages
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+-----------------------------------
 
-For Debian GNU/Linux and Ubuntu we provide packages in our APT repository.
+Debian GNU/Linux
+^^^^^^^^^^^^^^^^
 
-For Debian Wheezy add the following lines to ``/etc/apt/sources.list`` file:
+For Debian 7.x (Wheezy) we provide packages in our APT repository. To use
+our repository add the following lines to file ``/etc/apt/sources.list``:
 
 ``deb http://apt.dev.grnet.gr wheezy/``
 
 ``deb-src http://apt.dev.grnet.gr wheezy/``
 
-For Ubuntu 12.04 LTS add the following lines:
+After you update ``/etc/apt/sources.list`` import the repo's GPG key:
+
+.. code-block:: console
+
+  # curl https://dev.grnet.gr/files/apt-grnetdev.pub | apt-key add -
+
+To install the package use the following commands:
+
+.. code-block:: console
+
+  # apt-get update
+  # apt-get install snf-image
+
+The last command will also download and install the *snf-image-helper* image in
+the post install phase of the package installation.
+
+Ubuntu
+^^^^^^
+
+For Ubuntu 12.04 LTS we provide packages in our APT repository. To use our
+repository add the following lines to file ``/etc/apt/sources.list``:
 
 ``deb http://apt.dev.grnet.gr precise/``
 
@@ -40,8 +62,31 @@ To install the package use the following commands:
 The last command will also download and install the *snf-image-helper* image in
 the post install phase of the package installation.
 
+CentOS
+^^^^^^
+
+For CentOS 6.5 we provide packages in our Yum repository.
+
+To add the GRNET repository in your system, run:
+
+.. code-block:: console
+
+  # yum localinstall https://dev.grnet.gr/files/grnet-repo.rpm
+
+You can verify the authenticity of the package using our public key found
+`here <https://dev.grnet.gr/files/apt-grnetdev.pub>`_.
+
+To install snf-image run:
+
+.. code-block:: console
+
+  # yum install snf-image
+
+The last command will also download and install the *snf-image-helper* image in
+the post install phase of the package installation.
+
 Installing snf-image from source
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+--------------------------------
 
 To install snf-image from source, download the provided source package: