Update INSTALL.md

INSTALL.md

@@ -1,4 +1,73 @@
-Installation Instructions
+Simple Installation Instructions
 ==
+Shairport Sync can be installed in lots of different Linux and Unix machines, and there are lots of variations to consider -- see the [README.md](https://github.com/mikebrady/shairport-sync/blob/master/README.md) page for a fuller discussion. But here are really simple instructions for building and installing it on a Raspberry Pi B, 2B, 3B or 3B+. It is assumed that the Pi is running Raspbian Stretch Lite -- a GUI isn't needed, since Shairport Sync runs as a daemon program.
 
-Please refer to README.md for installation instructions.
+### Configure and Update
+Do the usual update and upgrade:
+```
+# apt-get update
+# apt-get upgrade
+# rpi-update
+``` 
+(Separately, if you haven't done so already, consider using the `raspi-config` tool to expand the file system to use the entire card.)
+
+### Activate the Improved Audio Driver
+Check the file `/boot/config.txt` and, if it's not there already, edit it to add the following line:
+```
+audio_pwm_mode=2
+```
+Reboot.
+
+### Remove Old Copies
+Before you begin building Shairport Sync, it's best to search and remove any existing copies. Use the command `$ which shairport-sync` to find them. For example, if `shairport-sync` has been installed previously, this might happen:
+```
+$ which shairport-sync
+/usr/local/bin/shairport-sync
+$ sudo rm /usr/local/bin/shairport-sync
+...
+```
+Do this until no more are found.
+
+### Build and Install
+Okay,now let's get the tools and sources for building and installing Shairport Sync.
+
+First, install the packages needed by Shairport Sync:
+```
+# apt-get install build-essential git xmltoman autoconf automake libtool libdaemon-dev libpopt-dev libconfig-dev libasound2-dev avahi-daemon libavahi-client-dev libssl-dev
+```
+Next, download Shairport Sync, configure it, compile and install it:
+```
+$ git clone https://github.com/mikebrady/shairport-sync.git
+$ cd shairport-sync
+$ autoreconf -fi
+$ ./configure --sysconfdir=/etc --with-alsa --with-avahi --with-ssl=openssl --with-systemd
+$ make
+$ sudo make install
+```
+
+Now to comfigure Shairport Sync.
+Here are the important options for the Shairport Sync configuration file at `/etc/shairport-sync.conf`:
+```
+// Sample Configuration File for Shairport Sync on a Raspberry Pi using the built-in audio DAC
+general =
+{
+  drift_tolerance_in_seconds = 0.010;
+  volume_range_db = 50;
+};
+
+alsa =
+{
+	output_device = "hw:0";
+  mixer_control_name = "PCM";
+};
+
+```
+Fourth, enable Shairport Sync to start automatically on boot up:
+```
+$ sudo systemctl enable shairport-sync
+```
+Fifth, either reboot the Pi or start the service:
+```
+$ sudo systemctl start shairport-sync
+```
+Sixth, enjoy!