Network setup

Back to Robobot B

WiFi network

If you are at DTU and the small display shows an IP, then all is fine. Otherwise read further down.

Network Manager

The NetworkManager uses device UUID as part of the Wi-Fi network setup. This means that (sometimes) an SD card can not be moved from one robot to another with a functional Wi-Fi connection.

After 20 seconds, an attempt to solve this is activated using the commands below (the code is found in svn/robobot/setup/rename_host.bash - last half).

Use the last line to setup manually - or the GUI, if available.

See the current network settings

nmcli dev show

Network manager connection with UUID

nmcli connection

List available wifi access points

nmcli dev wifi

Connect to DTUdevice net

You can establish a new connection from the command line

sudo nmcli device wifi connect DTUdevice password <password> ifname wlan0 ipv6.method "disabled"

This should create a new system-connection file with a usable UUID. IPv6 is disabled, as many of the IPv6 MACs seem to be the same (we cloned the SD card), and this will blacklist the connection for stealing the MAC.

There is a terminal-based user interface to edit a connection. First list connections:

$ nmcli con show
eg: NAME            UUID                                  TYPE      DEVICE 
preconfigured       e07a0ae8-028b-4d65-806c-ec63f435df44  wifi      wlan0  
lo                  2737bad6-956f-4668-99e0-4697f4ec30a7  loopback  lo 

Find the NAME of the connection to edit, e.g. 'preconfigured'

sudo nmtui edit "preconfigured"

The edit as desired.

Reload Network Manager to read this.

sudo nmcli connection reload

or restart the NetworkManager

sudo systemctl restart NetworkManager.service

Home network connection

If you know the SSID and password, you can prepare the robot for another (home) network. Use this command (replacing <SSID> and <password>):

sudo nmcli device wifi connect <SSID> password <password> ifname wlan0

If you have no network contact, then use a local link (cable) or attach a screen and keyboard.

Cable connection

Using static IP and DNS server on Raspberry

Assign a static IP for the Raspberry:

sudo nmcli connection add con-name eth0-manual ifname eth0 type ethernet ip4 192.168.7.7/24 ipv6.method disabled

The IP for the Raspberry is 192.168.7.1 when a cable is connected and the Network manager is reloaded.

sudo nmcli con reload

Install DNS server on Raspberry

Allow the connected PC to get an IP automatically; install DNSMASQ

sudo apt install dnsmasq

Configure the use by editing /etc/dnsmasq.conf

sudo nano /etc/dnsmasq.conf

Uncomment and change two lines. It is to be used on ETH0 only and in the IP range 192.168.7.50 to 192.168.7.99.

# DNS requests only on
# specified interface
interface=eth0
# range of addresses available for lease and optionally
# a lease time
dhcp-range=192.168.7.50,192.168.7.99,255.255.255.0,12h

Restart the dnsmasq

sudo service dnsmasq restart

To see the status of the dnsmasq service use:

journalctl -b0 -u dnsmasq.service

After this, when you plug in a cable to a PC, then, after some seconds, both the robot and the PC should have an IP in the range 192.168.7.x. And the robot should display the new IP 192.168.7.7.

You can now access the robot using

ssh local@192.168.7.7

Local link

Note: This method failed in most cases

If wifi is too slow or unavailable, a local link using a network cable could be the solution.

Many PCs will assign a local link IP like 168.254.x.x, and the Robot will do the same. The robot IP will be displayed on the small display but may be obscured if a Wi-Fi IP is available.

To prepare this behaviour, log in to the Raspberry using wifi (or attach a screen and keyboard) and make a preferred local-link cabled connection:

sudo nmcli con mod "Wired connection 1" ipv4.method link-local ipv6.method disabled

This should then be the behaviour after a reboot. "Wired connection 1" needs to be spelt this way; see the valid names using:

nmcli connection

Reload Network manager

sudo nmcli connection reload

Check IP and SSID

When the Pi has rebooted, connect to it using SSH once again. Check that the Pi is connected to WiFi

ifconfig

Under wlan0 confirm that the Pi has received an IP (inet addr) and note down the first three sections of the IP - they are most likely 10.197.21x.xxx

To see which SSID you are connected to, use

iwconfig

or

nmcli -o

The MAC address ('HWaddr' or 'ether') of the Pi should also be noted down - this probably starts with B8:27:EB:xx:xx:xx make sure to get all of it.

Find IP of robot (Linux)

In case the Pi gets a new IP address after reboot, you can search for it using the MAC address and nmap. If nmap is not installed, start by installing it

sudo apt-get install nmap

To search for the Pi using the MAC address in terminal type

nmap -sP 10.197.218.0/20 | awk '/^Nmap/{ip=$NF}/B8:27:EB:23:A0:F5/{print ip}'

where 10.197.218 is the first three sections of the IP you noted down, 20 is the number of fixed bits (out of 32), and B8:27:EB:23:A0:F5 is the MAC address of the Pi. This should return the IP of the Pi.

NB! the MAC can hold letters, they should probably be capital.

If you don't know the IP address

Use the first part to get a list of active IPs on the net:

 nmap -sP 10.197.218.0/24

The robot's name should be included in the list, but the network may take a while to detect it.

NTP

Network Time Protocol is used to keep clocks in sync. Raspberry Pi will start with the date and time of the last proper shutdown, and some seconds after the internet is up, it will sync the clock using NTP.

NTP need to be installed, i.e. 'sudo apt install ntp' if not done already.

At DTU most clock sources are blocked, the clock source needs to be configured.

At DTU, edit /etc/NTP.conf or /etc/ntpsec/ntp.conf and add ntp.ait.du.dk to the top of the server pool list.

sudo nano /etc/ntpsec/ntp.conf

...
# Use servers from the NTP Pool Project. Approved by Ubuntu Technical Board
# on 2011-02-08 (LP: #104525). See http://www.pool.ntp.org/join.html for
# more information.
pool ntp.ait.dtu.dk
...

Sync time (if on DTU net)

sudo ntpdate -u ntp.ait.dtu.dk

Should work in and around DTU - see also NTP howto for more details.

You can also check the status of the ntp service:

sudo systemctl status ntp.service