If you cannot connect to guruplug for some reason via lan interface, for example sshd stopped running or just firewalled yourself out of it, you can connect to it using serial connection.
When making order guruplug from original site , by adding few more bucks you can get development kit.
For connection in linux you can use small program called minicom.
You can find it in your distro repository.
$ sudo apt-get install minicom
Now connect your devkit to your computer using mini usb cable.
You should get output something like this:
[13997.188105] usb 3-1: new full speed USB device number 3 using uhci_hcd
[13997.408410] usb 3-1: Ignoring serial port reserved for JTAG
[13997.413595] ftdi_sio 3-1:1.1: FTDI USB Serial Device converter detected
[13997.413792] usb 3-1: Detected FT2232C
[13997.413807] usb 3-1: Number of endpoints 2
[13997.413820] usb 3-1: Endpoint 1 MaxPacketSize 64
[13997.413833] usb 3-1: Endpoint 2 MaxPacketSize 64
[13997.413845] usb 3-1: Setting MaxPacketSize 64
[13997.416502] usb 3-1: FTDI USB Serial Device converter now attached to ttyUSB0
On last line you can see, that device is attached as “ttyUSB0”.
We’ll use it in minicom settings.
Lets start the minicom (-s stands for “setup”)
$ minicom -s
Press letter “A”, to change Serial device, and enter address of your devkit.
if you had ttyUSB0, then you should write /dev/ttyUSB0 and press enter.
Then press letter “E” to change “Bps/Par/Bits” settings.
In opened window press letters “E” (speed 115200) and “Q” (Parity “none”, Data – 8, Stop bits – 1), then press enter.
By pressing letters “F” and “G” make sure that Flow control settings are both set to “off”.
If it’s all done, just press enter to get back to previous menu.
Press “Exit” (Do not press “Exit from minicom”!!! As it will exit from minicom program).
If you want to save it as default settings, you need to start minicom as root (“sudo minicom -s”).
To quit from minicom program, you have to press
ctrl+A then Z and X