Raspberry Pi computing cluster, Part 1
There are multiple ways to create a local area network (LAN) for Raspberry Pi computing cluster (RPCC). One of them is to assign a static IP address to each of Raspberry Pi computing unit in the RPCC and then use the RPCC’s computing units via these addresses through the Linux terminal. Here are the steps.
First, one needs to have a network switch that functions as a network bus for managing data traffic within the cluster. After the switch is available, all of the Raspberry Pi computing units can be connected to it using appropriate Ethernet cable. One end of the cable to the Ethernet port of the Pis and one end to appropriate port of the switch.
The cluster doesn’t need electricity yet, but the electricity connections can be made ready by connecting the micro-USB ports of the Pis to extension cord with multiple sockets. After this, the RPCC is pretty much setup hardware-wise and the setup should be like in the following diagram, where $\text{\texttt{RPI0}$N$}$ is hostname for $N$th computing unit, thick lines are Ethernet cable connections and “$\text{E}$” is connection to the electric grid:
Now the operating systems of the computing units can be configured. The RPCC under development uses eight units of Raspberry Pi 1 Model B+ as the computing units, so this means eight repetitions of flashing the headless Raspberry Pi OS (32-bit) to eight $16$ Gb MicroSD cards with the Raspberry Pi Imager. At the Imager’s user interface only computing unit’s hostname, user name and user password needs to be configured. Simple naming scheme to go along with appropriate IP addresses are:
Unit Username Passwd Hostname IP address
1 admin admin RPI00 192.168.1.100
2 admin admin RPI01 192.168.1.101
3 admin admin RPI02 192.168.1.102
4 admin admin RPI03 192.168.1.103
5 admin admin RPI04 192.168.1.104
6 admin admin RPI05 192.168.1.105
7 admin admin RPI06 192.168.1.106
8 admin admin RPI07 192.168.1.107
The freshly Raspberry Pi OS flashed MicroSD cards are now ready to be inserted into each MicroSD card slot at opposite side and just under the Pis’ USB and Ethernet ports of the Pis motherboard. Electricity can be turned on now.
After connecting RPI00 to screen via HDMI allows for doing
necessary configurations for the computing unit’s command line
after the the computing unit has booted up. This includes
expanding the computing unit’s file system, other possible
configurations, if needed, and setting up the connection using the
NetworkManager.
Example command for doing this is
nmcli con add type ethernet \
ifname eth0 \
con-name Ethernet-RPI00 \
ipv4.method manual \
ipv4.address 192.168.1.100/24 \
ipv4.gateway 192.168.1.1
Interface name (ifname) of RPI00 is found out by running the
command at the unit’s terminal:
nmcli show dev
and reading the value of GENERAL.DEVICE, which was the eth0.
One can use the above nmcli con add command for configuring the
computing units from RPI01 to RPI07, modifying the
ipv4.address’ value according the naming scheme described above.
Finally the laptop can be connected to the RPCC using the variation of the above command:
nmcli con add type ethernet \
ifname [NET-DEV-NAME] \
con-name Ethernet-RPCC \
ipv4.method manual \
ipv4.address 192.168.1.99/24 \
ipv4.gateway 192.168.1.1
where the [NET-DEV-NAME] is the name of laptop’s network device.
Since my laptop does not have Ethernet port, I used USB-to-Ethernet
dongle to add a Ethernet “card” to my laptop, figured
out the dongles name with the nmcli show dev command and replaced
the [NET-DEV-NAME] with a proper value.
To check that the laptop can connect to any device in the cluster,
one can open a SSH-connection to RPI00 by typing the
command
ssh [email protected]
to laptop’s terminal. RPI00 replies to the command by sending a
prompt for password. After typing in the password admin one is
logged into RPI00 and the RPCC network configuration is
sufficiently done for now.