Write device init help page

lib/actions/device.coffee

@@ -142,9 +142,31 @@ exports.init =
 	signature: 'device init [device]'
 	description: 'initialise a device with resin os'
 	help: '''
-		Device init.
+		Use this command to download the OS image of a certain application and write it to an SD Card.
 
-		TODO: Help page
+		Note that this command requires admin privileges.
+
+		If `device` is omitted, you will be prompted to select a device interactively.
+
+		Notice this command asks for confirmation interactively.
+		You can avoid this by passing the `--yes` boolean option.
+
+		You can quiet the progress bar by passing the `--quiet` boolean option.
+
+		You may have to unmount the device before attempting this operation.
+
+		You need to configure the network type and other settings:
+
+		Ethernet:
+			You can setup the device OS to use ethernet by setting the `--network` option to "ethernet".
+
+		Wifi:
+			You can setup the device OS to use wifi by setting the `--network` option to "wifi".
+			If you set "network" to "wifi", you will need to specify the `--ssid` and `--key` option as well.
+
+		Examples:
+			$ resin device init --application 91 --network ethernet
+			$ resin device init /dev/disk2 --application 91 --network wifi --ssid MyNetwork --key secret
 	'''
 	options: [
 		commandOptions.application

lib/helpers/helpers.coffee

@@ -1,3 +1,4 @@
+os = require('os')
 _ = require('lodash')
 getStdin = require('get-stdin')