Add SD card installation guide.

Signed-off-by: Volker Theile <volker.theile@openmediavault.org>

installation/index.rst

@@ -19,6 +19,7 @@ Installation variants:
     * :doc:`Dedicated drive </installation/via_iso>` - Adviced method via ISO image. This runs |omv| from its own drive.
     * :doc:`USB flash drive </installation/on_usb>` - This runs |omv| from a USB flash drive.
     * :doc:`Debian OS </installation/on_debian>` - This runs |omv| on top of an existing Debian OS.
+	* :doc:`SD card </installation/via_image>` - This runs |omv| from a SD card.
 
 First time use:
    If you have a screen attached, KVM or IMPI console the login screen will

installation/via_image.rst

@@ -0,0 +1,15 @@
+.. _installation_index:
+
+Installation via images
+#######################
+
+Prepare the image
+-----------------
+	`Etcher <https://etcher.io/>`_ can also be used to transfer ARM images
+	into SD cards.
+
+Boot the installer
+------------------
+	ARM images are ready to go, so boot from SD card and wait for the initial
+	setup to complete. This takes around 30 minutes in slow devices like
+	Raspberry PI.

installation/via_iso.rst

@@ -11,15 +11,12 @@ Burn the installer
 	$ sudo dd if=xxx.iso of=/dev/sdX bs=4096
 
 	If you have a CD-DVD burner, you can burn the ISO into an optical media
-	then boot from CD or DVD. Etcher can also be used to transfer arm images
-	into SD cards.
+	then boot from CD or DVD.
 
 Boot the installer
 ------------------
 	For x86 architecture, enter BIOS configuration, select to boot either from
-	USB or CD and reboot. ARM images are ready to go, so boot from sd card and
-	wait for the initial setup to complete. This takes around 30 minutes in
-	slow devices like Raspberry PI.
+	USB or CD and reboot.
 
 Installer
 ---------