01. Click the time icon at the top of the screen
02. Click on "Wifi"
03. Choose "Wifi Preferences"
04. Click the name of the router you're connected to (should have a blue checkmark next to it)
05. Toggle "Automatic IP Settings" to be Off
06. Input all of your IP settings into the fields below then click Done at the bottom.
Be sure that you take note of what your Subnet Address, Gateway address and DNS servers are so that you can put them in if they happen to get erased. You do know what the IP range for your router is though, right?
As for the root default password, I wish I knew. I tried using 'root' as the root password as well as my created one, and it didn't work. What you CAN do, is type "sudo su" in the command prompt and then type the password that you created and that should give you full rights to the system.
As for rootfs_open -w ... I have no idea what that command even does. :P