I recently needed to build Python 3.6 from source on the BeagleBone Black for a robotics project and discovered that the build would always fail after running out of memory. Who could have figured that 512MB of RAM wasn’t enough to build Python from source?! While I could have set up cross-compilation and performed the heavy lifting on my computer with more resources, I figured this was a perfect problem to solve by adding swap memory to the BeagleBone Black.

What is a swap space?

At a very high level, a swap space (usually in the form of a partition) allows the system to move some of the “lower priority” memory pages (blocks of memory) to the partition or file so that higher priority tasks can use the memory. The combined size of the physical memory and swap space is called virtual memory. Gary Sims has a great primer on swap spaces over at linux.com

In this case, the BeagleBone Black only has 512MB of RAM so I’ll be adding ~1GB of swap space to my SD card in the form of a swap file. This will allow it to perform more memory-intensive tasks without running out of memory (at a cost of slower access times).

Creating a swap file

Creating a swap space is a fairly simple process that involves creating a file (and filling it with zeros) then telling the system to use that file as a swap space. Finally, the system has to be configured to load that file on startup.

Check if you already have a swap file

sudo swapon -s

In my case I already created the file so it’s shown. The assumptions is that you’re performing these steps because you don’t have a swap space.

Create the swap file

Use the dd utility to create a file with a fixed size and fill it with “zeroes”. In this case I’m moving 1000 “zeroes” from /dev/zero in block sizes of 1024k (1MB) into my file at /var/cache/swap/swapfile. This will result in a swap file of around 1 gigabyte. Keep in mind that the swap file is actually named “swapfile” with no extension.

sudo dd if=/dev/zero of=/var/cache/swap/swapfile bs=1024k count=1000

use chmod to change the file permissions of the new swap file.

sudo chmod 0600 /var/cache/swap/swapfile

Use the mkswap  command to create the swap area using our newly created swap file.

sudo mkswap /var/cache/swap/swapfile

Finally, enable the swap area with the swapon command

sudo swapon /var/cache/swap/swapfile

Configure the swap file to automatically mount on boot

Open up the /etc/fstab file with the nano editor.

sudo nano /etc/fstab

Append the following line to the file:

/var/cache/swap/swapfile    none   swap   sw   0   0

That is all there is to it for this specific case – adding swap memory to the BeagleBone Black is pretty straightforward!

The post Adding Swap Memory to the Beaglebone Black appeared first on Paul Bupe Jr, PhD.

By default Cloud9 launches a workspace at /usr/lib/cloud9, which has useful examples and scripts for all sorts of applications. I want it to point, instead, to my personal projects folder so I’ll change the default Cloud9 workspace on the BeagleBone Black to /home/debian/projects.

Override systemd Service

Cloud9 is launched by /lib/systemd/system/cloud.service which explicitly starts the server pointing to /var/ib/cloud9.

In order to change this, we simply need to override the service with one that points to our desired directory. Packages generally install services in /lib/systemd/system while our new override will reside in /etc/systemd/system.

Step 1:

systemctl edit cloud9

This creates our override in /etc/systemd/system/cloud9.service.d/override.conf and opens up the file for editing. Then we simply clear ExecStart (since it is additive) and provide the new directory in that file.

[Service]
ExecStart=
ExecStart=/usr/bin/nodejs server.js --packed -w /home/debian/projects

Step 2:

Perform a daemon reload and restart the cloud9 service

systemctl daemon-reload
systemctl restart cloud9

Step 3:

Restart the browser. The new folder should now be the default workspace!

View my tutorial on setting up internet over USB on the BeagleBone Black.

The post Change the Default Cloud9 Workspace on the BeagleBone Black appeared first on Paul Bupe Jr, PhD.

Connecting a BeagleBone Black (BBB) to the internet over USB is a simple process thanks to the internet sharing capabilities of Windows. This is extremely convenient when developing because it allows your BeagleBone Black to have an internet connection as long as your computer or laptop has one, no matter the network, and SSH access over a single USB cable.

Windows Configuration

These instructions assume you have already installed an image on your BBB and can connect to the web interface. If not, the official documentation is extremely thorough and easy to follow.

Step 1: Configure your primary network interface for sharing.

Open the Run prompt (Win+R) and enter ncpa.cpl to open Network Connections.

You should see (in addition to your regular network connection) a new connection with a description that starts with “Linux USB Ethernet” or something similar. This is your BBB’s connection.

Right click on the internet connection your want to share (not on the BBB connection) and click on Properties. In the properties window click on the Sharing tab and check the box that says Allow other network users to connect through this computer’s Internet connection. Select the BBB’s connection under the Home networking connection: dropdown then click OK to save.

Double click on the BBB’s connection and click on Internet Protocol Version 4 (TCP/IPv4) to highlight it then click on Properties. Alternatively you can just double click on the text (not the checkbox).

Fill in the IP address and DNS information as shown in the image. The BBB will expect the computer to have an IP address of 192.168.7.1 and it will use the computer as a gateway to the internet.

That’s all the setup needed on the Windows machine!

Step 2: BeagleBone Black Configuration

All of the configuration needed on the BBB is in a single file. Interestingly, all the tutorials I’ve seen on this topic don’t show the proper way of configuring the network so that the changes are persistent.

SSH Access

The first step is to connect to the BBB via SSH. PuTTY is the de facto SSH client on Windows and I highly recommend it. Open up PuTTy and enter the BBB’s default IP address (192.169.7.2) then press Open. You may see a warning sign pop up if it’s the first time connecting to the IP but just click Yes and continue.

You’ll be asked for a login. The default credentials are:

login: debian
pass: temppwd

Be sure to change the password!

Note: When typing in the password, you will not see anything happening. That’s a security feature — just press enter when you enter the full password. 

Configuration

We will be editing the interfaces file, which is used to configure the network interfaces on the system as the name suggests. Enter the following command to open up the file for editing:

sudo nano /etc/network/interfaces

sudo ( originally called “superuser do”) temporarily elevates the security privileges of the debian user to the superuser so that it can modify system files. You will be asked to enter the user password which is temppwd in the default case. nano is a simple text editor that’s present on most Linux systems.

Once in the file, use the down arrow key or Page Down key to go to the bottom of the file where you should see entries for the usb0 interface. Enter the following information:

iface usb0 inet static
    address 192.168.7.2
    netmask 255.255.255.252
    network 192.168.7.0
    gateway 192.168.7.1
    dns-nameservers 8.8.8.8
    post-up route add default gw 192.168.7.1

When the system starts up, the system runs a configuration script located at /opt/scripts/boot/autoconfigure_usb0.sh
that reads this /etc/network/interfaces file and sets the IP address and netmask for the usb0 interface.

The configuration script also reads the dns-nameservers value and writes it to /etc/resolv.conf. Lastly, the script executes the post-up value line after the network interface is up (thus the name) in order to add the default gateway (which is the IP address we set on the Windows machine) to the route.

After making the changes, press CTRL+O to save the changes then CTRL+X to close the file. Reboot the system with:

sudo reboot

After the reboot is complete, connect to the system again (you can just right-click anywhere on the PuTTy window and click on Restart session).

The route command will show you if the gateway is set.

route

The /etc/resolv.conf file should also contain the nameserver entry.

cat /etc/resolv.conf

That’s all the configuration needed to get internet over USB working! You can test it out by pinging Google with ping google.com. You can press CTRL+C to stop the ping command.

The post Connecting a BeagleBone Black to the Internet over USB appeared first on Paul Bupe Jr, PhD.