apt docs initial checkin (#7)

Signed-off-by: Theo Weiss <theo@m1theo.org> (github: theoweiss)

installation/apt.md

@@ -6,4 +6,119 @@ layout: documentation
 
 # Installation on Linux through APT
 
-to be done...
+1.  Install prerequisites 
+
+1.  Add the openHAB Bintray Repositories key to the apt-keyring
+
+    - with wget:
+
+    ```
+    wget -qO - 'https://bintray.com/user/downloadSubjectPublicKey?username=openhab' | sudo apt-key add -
+    ```
+
+    - or with curl:
+
+    ```
+    curl 'https://bintray.com/user/downloadSubjectPublicKey?username=openhab' | sudo apt-key add -
+    ```
+
+1.  Add openHAB apt repository to the apt sources list (Note: the current openhab.list file will be overwritten)
+    - To install a beta releases use:
+
+    ```
+    echo 'deb http://dl.bintray.com/openhab/apt-repo2 testing main' | sudo tee /etc/apt/sources.list.d/openhab.list
+    ```
+
+    - For stable releases use:
+
+    ```
+    echo "deb http://dl.bintray.com/openhab/apt-repo2 stable main" | sudo tee /etc/apt/sources.list.d/openhab.list
+    ```
+
+1.  Resynchronize the package index
+
+    ```
+    sudo apt-get update
+    ```
+
+1.  Install openHAB
+    - Either use the offline distribution which is full blown and comes with all addons. Additional addons will be 
+    installed an request from your local disk.
+
+    ```
+    sudo apt-get install openhab2-offline
+    ```
+
+    - Or the online distribution which will install additional addons on request from the internet.
+
+    ```
+    sudo apt-get install openhab2-online
+    ```
+
+1.  Start openHAB - manually
+
+    - Init based on sysVinit (e.g. Debian 7 / Ubuntu 14.x and earlier)
+
+    ```
+    sudo /etc/init.d/openhab2 start
+    sudo /etc/init.d/openhab2 status
+    ```
+
+    - Init based on systemd (e.g. Debian 8 / Ubuntu 15.x and newer)
+
+    ```
+    sudo systemctl start openhab2
+    ```
+
+1. Start openHAB - at system startup
+
+    - Init based on sysVinit (e.g. Debian 7 / Ubuntu 14.x and earlier)
+
+    ```
+    sudo update-rc.d openhab2 defaults
+    ```
+
+    - or using Init based on systemd (e.g. Debian 8 / Ubuntu 15.x and newer)
+
+    ```
+    sudo systemctl daemon-reload
+    sudo systemctl enable openhab2
+    ```
+
+# To Upgrade
+Note: changed configuration files will be retained even on upgrades.
+
+    sudo apt-get update
+    sudo apt-get upgrade
+
+# File locations
+* **service configuration** /etc/default/openhab2
+* **site configuration**  /etc/openhab2
+* **log files**  /var/log/openhab2
+* **userdata like rrd4j databases**  /var/lib/openhab2 and subdirectories
+* **openHAB application**  /usr/share/openhab2
+
+
+# Advanced Setup - Apt Repository Distributions
+
+1. stable
+
+    The latest stable openHAB release will be installed.
+
+1. testing
+
+    The latest release candidate of openHAB will be installed.
+
+1. version based distribution names (2.0.0.b3, 2.0.0, ...)
+
+    All Releases are available as with a distribution name corresponding to the version name.
+If you want to stick your installation to a specific version use one of these distribution names.
+The installation will only be upgraded if you change the sources.list to another version.
+Therefore "apt-get update && apt-get upgrade" can be safely used for the other linux software.
+
+    Examples:
+
+    ```
+    echo "deb https://dl.bintray.com/openhab/apt-repo2 2.0.0.b3 main" | sudo tee -a /etc/apt/sources.list
+    echo "deb https://dl.bintray.com/openhab/apt-repo 2.0.0 main" | sudo tee -a /etc/apt/sources.list
+    ```