This is the latest (main) BeagleBoard documentation. If you are looking for stable releases, use the drop-down menu on the bottom-left and select the desired version.

Beyond the Basics

In Basics, you learned how to set up BeagleBone Black, and Sensors, Displays and Other Outputs, and Motors showed how to interface to the physical world. The remainder of the book moves into some more exciting advanced topics, and this chapter gets you ready for them.

The recipes in this chapter assume that you are running Linux on your host computer (Selecting an OS for Your Development Host Computer) and are comfortable with using Linux. We continue to assume that you are logged in as debian on your Bone.

Running Your Bone Standalone

Problem

You want to use BeagleBone Black as a desktop computer with keyboard, mouse, and an HDMI display.

Solution

The Bone comes with USB and a microHDMI output. All you need to do is connect your keyboard, mouse, and HDMI display to it.

To make this recipe, you will need:

  • Standard HDMI cable and female HDMI-to-male microHDMI adapter, or

  • MicroHDMI-to-HDMI adapter cable

  • HDMI monitor

  • USB keyboard and mouse

  • Powered USB hub

Note

The microHDMI adapter is nice because it allows you to use a regular HDMI cable with the Bone. However, it will block other ports and can damage the Bone if you aren’t careful. The microHDMI-to-HDMI cable won’t have these problems.

Tip

You can also use an HDMI-to-DVI cable and use your Bone with a DVI-D display.

The adapter looks something like Female HDMI-to-male microHDMI adapter.

HDMI Adaptor

Fig. 211 Female HDMI-to-male microHDMI adapter

Plug the small end into the microHDMI input on the Bone and plug your HDMI cable into the other end of the adapter and your monitor. If nothing displays on your Bone, reboot.

If nothing appears after the reboot, edit the /boot/uEnv.txt file. Search for the line containing disable_uboot_overlay_video=1 and make sure it’s commented out:

###Disable auto loading of virtual capes (emmc/video/wireless/adc)
#disable_uboot_overlay_emmc=1
#disable_uboot_overlay_video=1

Then reboot.

The /boot/uEnv.txt file contains a number of configuration commands that are executed at boot time. The # character is used to add comments; that is, everything to the right of a +# is ignored by the Bone and is assumed to be for humans to read. In the previous example, ###Disable auto loading is a comment that informs us the next line(s) are for disabling things. Two disable_uboot_overlay commands follow. Both should be commented-out and won’t be executed by the Bon

Why not just remove the line? Later, you might decide you need more general-purpose input/output (GPIO) pins and don’t need the HDMI display. If so, just remove the # from the disable_uboot_overlay_video=1 command. If you had completely removed the line earlier, you would have to look up the details somewhere to re-create it.

When in doubt, comment-out don’t delete.

Note

If you want to re-enable the HDMI audio, just comment-out the line you added.

The Bone has only one USB port, so you will need to get either a keyboard with a USB hub or a USB hub. Plug the USB hub into the Bone and then plug your keyboard and mouse in to the hub. You now have a Beagle workstation no host computer is needed.

Tip

A powered hub is recommended because USB can supply only 500 mA, and you’ll want to plug many things into the Bone.

This recipe disables the HDMI audio, which allows the Bone to try other resolutions. If this fails, see BeagleBoneBlack HDMI for how to force the Bone’s resolution to match your monitor.

Selecting an OS for Your Development Host Computer

Problem

Your project needs a host computer, and you need to select an operating system (OS) for it.

Solution

For projects that require a host computer, we assume that you are running Linux Ubuntu 20.04 LTS. You can be running either a native installation, through Windows Subsystem for Linux, via a virtual machine such as VirtualBox, or in the cloud (Microsoft Azure or Amazon Elastic Compute Cloud, EC2, for example).

Recently I’ve been preferring Windows Subsystem for Linux.

Getting to the Command Shell via SSH

Problem

You want to connect to the command shell of a remote Bone from your host pass:[<span class=”keep-together”>computer</span>].

Solution

Running Python and JavaScript Applications from Visual Studio Code shows how to run shell commands in the Visual Studio Code bash tab. However, the Bone has Secure Shell (SSH) enabled right out of the box, so you can easily connect by using the following command to log in as user debian, (note the $ at the end of the prompt):

host$ ssh debian@192.168.7.2
Warning: Permanently added 'bone,192.168.7.2' (ECDSA) to the list of known hosts.
Last login: Mon Dec 22 07:53:06 2014 from yoder-linux.local
bone$

debian has the default password tempped It’s best to change the password:

bone$ password
Changing password for debian.
(current) UNIX password:
Enter new UNIX password:
Retype new UNIX password:
password: password updated successfully

Getting to the Command Shell via the Virtual Serial Port

Problem

You want to connect to the command shell of a remote Bone from your host computer without using SSH.

Solution

Sometimes, you can’t connect to the Bone via SSH, but you have a network working over USB to the Bone. There is a way to access the command line to fix things without requiring extra hardware. (Viewing and Debugging the Kernel and u-boot Messages at Boot Time shows a way that works even if you don’t have a network working over USB, but it requires a special serial-to-USB cable.)

First, check to ensure that the serial port is there. On the host computer, run the following command:

host$ ls -ls /dev/ttyACM0
0 crw-rw---- 1 root dialout 166, 0 Jun 19 11:47 /dev/ttyACM0

/dev/ttyACM0 is a serial port on your host computer that the Bone creates when it boots up. The letters crw-rw—- show that you can’t access it as a normal user. However, you can access it if you are part of dialout group. See if you are in the dialout group:

host$ groups
yoder adm tty uucp dialout cdrom sudo dip plugdev lpadmin sambashare

Looks like I’m already in the group, but if you aren’t, just add yourself to the group:

host$ sudo adduser $USER dialout

You have to run adduser only once. Your host computer will remember the next time you boot up. Now, install and run the screen command:

host$ sudo apt install screen
host$ screen /dev/ttyACM0 115200
Debian GNU/Linux 7 beaglebone ttyGS0

default username:password is [debian:temppwd]

Support/FAQ: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian

The IP Address for usb0 is: 192.168.7.2
beaglebone login:

The /dev/ttyACM0 parameter specifies which serial port to connect to, and 115200 tells the speed of the connection. In this case, it’s 115,200 bits per second.

Viewing and Debugging the Kernel and u-boot Messages at Boot Time

Problem

You want to see the messages that are logged by BeagleBone Black as it comes to life.

Solution

There is no network in place when the Bone first boots up, so Getting to the Command Shell via SSH and Getting to the Command Shell via the Virtual Serial Port won’t work. This recipe uses some extra hardware (FTDI cable) to attach to the Bone’s console serial port.

To make this recipe, you will need:

  • 3.3 V FTDI cable

Warning

Be sure to get a 3.3 V FTDI cable (shown in FTDI cable), because the 5 V cables won’t work.

Tip

The Bone’s Serial Debug J1 connector has Pin 1 connected to ground, Pin 4 to receive, and Pin 5 to transmit. The other pins are not attached.

FTDI Cable

Fig. 212 FTDI cable

Look for a small triangle at the end of the FTDI cable (FTDI connector). It’s often connected to the black wire.

FTDI Connector

Fig. 213 FTDI connector

Next, look for the FTDI pins of the Bone (labeled J1 on the Bone), shown in FTDI pins for the FTDI connector. They are next to the P9 header and begin near pin 20. There is a white dot near P9_20.

Serial Debug Pins

Fig. 214 FTDI pins for the FTDI connector

Plug the FTDI connector into the FTDI pins, being sure to connect the triangle pin on the connector to the white dot pin of the FTDI connector.

Now, run the following commands on your host computer:

host$ ls -ls /dev/ttyUSB0
0 crw-rw---- 1 root dialout 188, 0 Jun 19 12:43 /dev/ttyUSB0
host$ sudo adduser $USER dialout
host$ screen /dev/ttyUSB0 115200
Debian GNU/Linux 7 beaglebone ttyO0

default username:password is [debian:temppwd]

Support/FAQ: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian

The IP Address for usb0 is: 192.168.7.2
beaglebone login:

Note

Your screen might initially be blank. Press Enter a couple times to see the login prompt.

Verifying You Have the Latest Version of the OS on Your Bone from the Shell

Problem

You are logged in to your Bone with a command prompt and want to know what version of the OS you are running.

Solution

Log in to your Bone and enter the following command:

bone$ cat /etc/dogtag
BeagleBoard.org Debian Bullseye IoT Image 2022-07-01

Verifying You Have the Latest Version of the OS on Your Bone shows how to open the ID.txt file to see the OS version. The /etc/dogtag file has the same contents and is easier to find if you already have a command prompt. See Running the Latest Version of the OS on Your Bone if you need to update your OS.

Controlling the Bone Remotely with a VNC

Problem

You want to access the BeagleBone’s graphical desktop from your host computer.

Solution

Run the installed Virtual Network Computing (VNC) server:

bone$ tightvncserver

You will require a password to access your desktops.

Password:
Verify:
Would you like to enter a view-only password (y/n)? n
xauth: (argv):1:  bad display name "beaglebone:1" in "add" command

New 'X' desktop is beaglebone:1

Creating default startup script /home/debian/.vnc/xstartup
Starting applications specified in /home/debian/.vnc/xstartup
Log file is /home/debian/.vnc/beagleboard:1.log

To connect to the Bone, you will need to run a VNC client. There are many to choose from. Remmina Remote Desktop Client is already installed on Ubuntu. Start and select the new remote desktop file button (Creating a new remote desktop file in Remmina Remote Desktop Client).

Create a new remote desktop

Fig. 215 Creating a new remote desktop file in Remmina Remote Desktop Client

Give your connection a name, being sure to select “Remmina VNC Plugin” Also, be sure to add :1 after the server address, as shown in Configuring the Remmina Remote Desktop Client. This should match the :1 that was displayed when you started vncserver.

Configuring

Fig. 216 Configuring the Remmina Remote Desktop Client

Click Connect to start graphical access to your Bone, as shown in The Remmina Remote Desktop Client showing the BeagleBone desktop.

Desktop

Fig. 217 The Remmina Remote Desktop Client showing the BeagleBone desktop

Tip

You might need to resize the VNC screen on your host to see the bottom menu bar on your Bone.

Note

You need to have X Windows installed and running for the VNC to work. Here’s how to install it. This needs some 250M of disk space and 19 minutes to install.

bone$ bone$ sudo apt install bbb.io-xfce4-desktop
bone$ cp /etc/bbb.io/templates/fbdev.xorg.conf /etc/X11/xorg.conf
bone$ startxfce4
/usr/bin/startxfce4: Starting X server
/usr/bin/startxfce4: 122: exec: xinit: not found

Learning Typical GNU/Linux Commands

Problem

There are many powerful commands to use in Linux. How do you learn about them?

Solution

Common Linux commands lists many common Linux commands.

Table 68 Common Linux commands

Command

Action

pwd

show current directory

cd

change current directory

ls

list directory contents

chmod

change file permissions

chown

change file ownership

cp

copy files

mv

move files

rm

remove files

mkdir

make directory

rmdir

remove directory

cat

dump file contents

less

progressively dump file

vi

edit file (complex)

nano

edit file (simple)

head

trim dump to top

tail

trim dump to bottom

echo

print/dump value

env

dump environment variables

export

set environment variable

history

dump command history

grep

search dump for strings

man

get help on command

apropos

show list of man pages

find

search for files

tar

create/extract file archives

gzip

compress a file

gunzip

decompress a file

du

show disk usage

df

show disk free space

mount

mount disks

tee

write dump to file in parallel

hexdump

readable binary dumps

whereis

locates binary and source files

Editing a Text File from the GNU/Linux Command Shell

Problem

You want to run an editor to change a file.

Solution

The Bone comes with a number of editors. The simplest to learn is nano. Just enter the following command:

bone$ nano file

You are now in nano (Editing a file with nano). You can’t move around the screen using the mouse, so use the arrow keys. The bottom two lines of the screen list some useful commands. Pressing ^G (Ctrl-G) will display more useful commands. ^X (Ctrl-X) exits nano and gives you the option of saving the file.

nano

Fig. 218 Editing a file with nano

Tip

By default, the file you create will be saved in the directory from which you opened nano.

Many other text editors will run on the Bone. vi, vim, emacs, and even eclipse are all supported. See Installing Additional Packages from the Debian Package Feed to learn if your favorite is one of them.

Establishing an Ethernet-Based Internet Connection

Problem

You want to connect your Bone to the Internet using the wired network connection.

Solution

Plug one end of an Ethernet patch cable into the RJ45 connector on the Bone (see The RJ45 port on the Bone) and the other end into your home hub/router. The yellow and green link lights on both ends should begin to flash.

RJ45

Fig. 219 The RJ45 port on the Bone

If your router is already configured to run DHCP (Dynamical Host Configuration Protocol), it will automatically assign an IP address to the Bone.

Warning

It might take a minute or two for your router to detect the Bone and assign the IP address.

To find the IP address, open a terminal window and run the ip command:

bone$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
   link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
   inet 127.0.0.1/8 scope host lo
      valid_lft forever preferred_lft forever
   inet6 ::1/128 scope host
      valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
   link/ether c8:a0:30:a6:26:e8 brd ff:ff:ff:ff:ff:ff
   inet 10.0.5.144/24 brd 10.0.5.255 scope global dynamic eth0
      valid_lft 80818sec preferred_lft 80818sec
   inet6 fe80::caa0:30ff:fea6:26e8/64 scope link
      valid_lft forever preferred_lft forever
3: usb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
   link/ether c2:3f:44:bb:41:0f brd ff:ff:ff:ff:ff:ff
   inet 192.168.7.2/24 brd 192.168.7.255 scope global usb0
      valid_lft forever preferred_lft forever
   inet6 fe80::c03f:44ff:febb:410f/64 scope link
      valid_lft forever preferred_lft forever
4: usb1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
   link/ether 76:7e:49:46:1b:78 brd ff:ff:ff:ff:ff:ff
   inet 192.168.6.2/24 brd 192.168.6.255 scope global usb1
      valid_lft forever preferred_lft forever
   inet6 fe80::747e:49ff:fe46:1b78/64 scope link
      valid_lft forever preferred_lft forever
5: can0: <NOARP,ECHO> mtu 16 qdisc no-op state DOWN group default qlen 10
   link/can
6: can1: <NOARP,ECHO> mtu 16 qdisc no-op state DOWN group default qlen 10
   link/can

My Bone is connected to the Internet in two ways: via the RJ45 connection (eth0) and via the USB cable (usb0). The inet field shows that my Internet address is 10.0.5.144 for the RJ45 connector.

On my university campus, you must register your MAC address before any device will work on the network. The HWaddr field gives the MAC address. For eth0, it’s c8:a0:30:a6:26:e8.

The IP address of your Bone can change. If it’s been assigned by DHCP, it can change at any time. The MAC address, however, never changes; it is assigned to your ethernet device when it’s manufactured.

Warning

When a Bone is connected to some networks it becomes visible to the world. If you don’t secure your Bone, the world will soon find it. See debian has the default password tempped It’s best to change the password: and Setting Up a Firewall

On many home networks, you will be behind a firewall and won’t be as visible.

Establishing a WiFi-Based Internet Connection

Problem

You want BeagleBone Black to talk to the Internet using a USB wireless adapter.

Solution

Tip

For the correct instructions for the image you are using, go to latest-images and click on the image you are using.

I’m running Debian 11.x (Bullseye), the middle one.

Latest Image Page

Fig. 220 Latest Beagle Images

Scroll to the top of the page and you’ll see instructions on setting up Wifi. The instructions here are based on using +networkctl+

Network Setup Instructions

Fig. 221 Instructions for setting up your network.

Several WiFi adapters work with the Bone. Check WiFi Adapters for the latest list.

To make this recipe, you will need:

  • USB Wifi adapter

  • 5 V external power supply

Warning

Most adapters need at least 1 A of current to run, and USB supplies only 0.5 A, so be sure to use an external power supply. Otherwise, you will experience erratic behavior and random crashes.

First, plug in the WiFi adapter and the 5 V external power supply and reboot.

Then run lsusb to ensure that your Bone found the adapter:

bone$ lsusb
Bus 001 Device 002: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n
WLAN Adapter
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Note

There is a well-known bug in the Bone’s 3.8 kernel series that prevents USB devices from being discovered when hot-plugged, which is why you should reboot. Newer kernels should address this issue.

Next, run networkctl to find your adapter’s name. Mine is called wlan0, but you might see other names, such as ra0.

bone$ networkctl
IDX LINK    TYPE     OPERATIONAL SETUP
1 lo      loopback carrier     unmanaged
2 eth0    ether    no-carrier  configuring
3 usb0    gadget   routable    configured
4 usb1    gadget   routable    configured
5 can0    can      off         unmanaged
6 can1    can      off         unmanaged
7 wlan0   wlan     routable    configured
8 SoftAp0 wlan     routable    configured

8 links listed.

If no name appears, try ip a:

bone$ ip a
...
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
   link/ether c8:a0:30:a6:26:e8 brd ff:ff:ff:ff:ff:ff
3: usb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
   link/ether c2:3f:44:bb:41:0f brd ff:ff:ff:ff:ff:ff
   inet 192.168.7.2/24 brd 192.168.7.255 scope global usb0
      valid_lft forever preferred_lft forever
   inet6 fe80::c03f:44ff:febb:410f/64 scope link
      valid_lft forever preferred_lft forever
...
7: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
   link/ether 64:69:4e:7e:5c:e4 brd ff:ff:ff:ff:ff:ff
   inet 10.0.7.21/24 brd 10.0.7.255 scope global dynamic wlan0
      valid_lft 85166sec preferred_lft 85166sec
   inet6 fe80::6669:4eff:fe7e:5ce4/64 scope link
      valid_lft forever preferred_lft forever


Next edit the configuration file */etc/wpa_supplicant/wpa_supplicant-wlan0.conf*.
bone$ sudo nano /etc/wpa_supplicant/wpa_supplicant-wlan0.conf

In the file you’ll see:

ctrl_interface=DIR=/run/wpa_supplicant GROUP=netdev
update_config=1
#country=US

network={
     ssid="Your SSID"
     psk="Your Password"
}

Change the ssid and psk entries for your network. Save your file, then run:

bone$ sudo systemctl restart systemd-networkd
bone$  ip a
bone$ ping -c2 google.com
PING google.com (142.250.191.206) 56(84) bytes of data.
64 bytes from ord38s31-in-f14.1e100.net (142.250.191.206): icmp_seq=1 ttl=115 time=19.5 ms
64 bytes from ord38s31-in-f14.1e100.net (142.250.191.206): icmp_seq=2 ttl=115 time=19.4 ms

--- google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 19.387/19.450/19.513/0.063 ms

wlan0 should now have an ip address and you should be on the network. If not, try rebooting.

Sharing the Host’s Internet Connection over USB

Problem

Your host computer is connected to the Bone via the USB cable, and you want to run the network between the two.

Solution

Establishing an Ethernet-Based Internet Connection shows how to connect BeagleBone Black to the Internet via the RJ45 Ethernet connector. This recipe shows a way to connect without using the RJ45 connector.

A network is automatically running between the Bone and the host computer at boot time using the USB. The host’s IP address is 192.168.7.1 and the Bone’s is 192.168.7.2. Although your Bone is talking to your host, it can’t reach the Internet in general, nor can the Internet reach it. On one hand, this is good, because those who are up to no good can’t access your Bone. On the other hand, your Bone can’t reach the rest of the world.

Letting your bone see the world: setting up IP masquerading

You need to set up IP masquerading on your host and configure your Bone to use it. Here is a solution that works with a host computer running Linux. Add the code in Code for IP Masquerading (ipMasquerade.sh) to a file called ipMasquerade.sh on your host computer.

Listing 36 Code for IP Masquerading (ipMasquerade.sh)
 1#!/bin/bash
 2# These are the commands to run on the host to set up IP 
 3#  masquerading so the Bone can access the Internet through 
 4#  the USB connection.
 5# This configures the host, run ./setDNS.sh to configure the Bone.
 6# Inspired by http://thoughtshubham.blogspot.com/2010/03/
 7#  internet-over-usb-otg-on-beagleboard.html
 8
 9if [ $# -eq 0 ] ; then
10echo "Usage: $0 interface (such as eth0 or wlan0)"
11exit 1
12fi
13
14interface=$1
15hostAddr=192.168.7.1
16beagleAddr=192.168.7.2
17ip_forward=/proc/sys/net/ipv4/ip_forward
18
19if [ `cat $ip_forward` == 0 ]
20  then
21    echo "You need to set IP forwarding. Edit /etc/sysctl.conf using:"
22    echo "$ sudo nano /etc/sysctl.conf"
23    echo "and uncomment the line   \"net.ipv4.ip_forward=1\""
24    echo "to enable forwarding of packets. Then run the following:"
25    echo "$ sudo sysctl -p"
26    exit 1
27  else
28    echo "IP forwarding is set on host."
29fi
30# Set up IP masquerading on the host so the bone can reach the outside world
31sudo iptables -t nat -A POSTROUTING -s $beagleAddr -o $interface -j MASQUERADE

ipMasquerade.sh

Then, on your host, run the following commands:

host$ chmod +x ipMasquerade.sh
host$ ./ipMasquerade.sh eth0

This will direct your host to take requests from the Bone and send them to eth0. If your host is using a wireless connection, change eth0 to wlan0.

Now let’s set up your host to instruct the Bone what to do. Add the code in Code for setting the DNS on the Bone (setDNS.sh) to setDNS.sh on your host computer.

Listing 37 Code for setting the DNS on the Bone (setDNS.sh)
 1#!/bin/bash
 2# These are the commands to run on the host so the Bone
 3#  can access the Internet through the USB connection.
 4# Run ./ipMasquerade.sh the first time. It will set up the host.
 5# Run this script if the host is already set up.
 6# Inspired by http://thoughtshubham.blogspot.com/2010/03/internet-over-usb-otg-on-beagleboard.html
 7
 8hostAddr=192.168.7.1
 9beagleAddr=${1:-192.168.7.2}
10
11# Save the /etc/resolv.conf on the Beagle in case we mess things up.
12ssh root@$beagleAddr "mv -n /etc/resolv.conf /etc/resolv.conf.orig"
13# Create our own resolv.conf
14cat - << EOF > /tmp/resolv.conf
15# This is installed by ./setDNS.sh on the host
16
17EOF
18
19TMP=/tmp/nmcli
20# Look up the nameserver of the host and add it to our resolv.conf
21# From: http://askubuntu.com/questions/197036/how-to-know-what-dns-am-i-using-in-ubuntu-12-04
22# Use nmcli dev list for older version nmcli
23# Use nmcli dev show for newer version nmcli
24nmcli dev show > $TMP
25if [ $? -ne 0 ]; then   # $? is the return code, if not 0 something bad happened.
26    echo "nmcli failed, trying older 'list' instead of 'show'"
27    nmcli dev list > $TMP
28    if [ $? -ne 0 ]; then
29        echo "nmcli failed again, giving up..."
30        exit 1
31    fi
32fi
33
34grep IP4.DNS $TMP | sed 's/IP4.DNS\[.\]:/nameserver/' >> /tmp/resolv.conf
35
36scp /tmp/resolv.conf root@$beagleAddr:/etc
37
38# Tell the beagle to use the host as the gateway.
39ssh root@$beagleAddr "/sbin/route add default gw $hostAddr" || true
40

setDNS.sh

Then, on your host, run the following commands:

host$ chmod +x setDNS.sh
host$ ./setDNS.sh
host$ ssh -X root@192.168.7.2
bone$ ping -c2 google.com
PING google.com (216.58.216.96) 56(84) bytes of data.
64 bytes from ord30s22....net (216.58.216.96): icmp_req=1 ttl=55 time=7.49 ms
64 bytes from ord30s22....net (216.58.216.96): icmp_req=2 ttl=55 time=7.62 ms

--- google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1002ms
rtt min/avg/max/mdev = 7.496/7.559/7.623/0.107 ms

This will look up what Domain Name System (DNS) servers your host is using and copy them to the right place on the Bone. The ping command is a quick way to verify your connection.

Letting the world see your bone: setting up port forwarding

Now your Bone can access the world via the USB port and your host computer, but what if you have a web server on your Bone that you want to access from the world? The solution is to use port forwarding from your host. Web servers typically listen to port 80. First, look up the IP address of your host:

host$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:e0:4e:00:22:51
          inet addr:137.112.41.35  Bcast:137.112.41.255  Mask:255.255.255.0
          inet6 addr: fe80::2e0:4eff:fe00:2251/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5371019 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4720856 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:1667916614 (1.6 GB)  TX bytes:597909671 (597.9 MB)

eth1      Link encap:Ethernet  HWaddr 00:1d:60:40:58:e6
...

It’s the number following inet addr:, which in my case is 137.112.41.35.

Tip

If you are on a wireless network, find the IP address associated with wlan0.

Then run the following, using your host’s IP address:

host$ sudo iptables -t nat -A PREROUTING -p tcp -s 0/0 \
     -d 137.112.41.35 --dport 1080 -j DNAT --to 192.168.7.2:80

Now browse to your host computer at port 1080. That is, if your host’s IP address is 123.456.789.0, enter 123.456.789.0:1080. The :1080 specifies what port number to use. The request will be forwarded to the server on your Bone listening to port 80. (I used 1080 here, in case your host is running a web server of its own on port 80.)

Setting Up a Firewall

Problem

You have put your Bone on the network and want to limit which IP addresses can access it.

Solution

How-To Geek has a great posting on how do use ufw, the “uncomplicated firewall”. Check out How to Secure Your Linux Server with a UFW Firewall. I’ll summarize the initial setup here.

First install and check the status:

bone$ sudo apt install ufw
bone$ sudo ufw status
Status: inactive

Now turn off everything coming in and leave on all outgoing. Note, this won’t take effect until ufw is enabled.

bone$ sudo ufw default deny incoming
bone$ sudo ufw default allow outgoing

Don’t enable yet, make sure ssh still has access

bone$ sudo ufw allow 22

Just to be sure, you can install nmap on your host computer to see what ports are currently open.

host$ sudo apt update
host$ sudo apt install nmap
host$ nmap 192.168.7.2
Starting Nmap 7.80 ( https://nmap.org ) at 2022-07-09 13:37 EDT
Nmap scan report for bone (192.168.7.2)
Host is up (0.014s latency).
Not shown: 997 closed ports
PORT     STATE SERVICE
22/tcp   open  ssh
80/tcp   open  http
3000/tcp open  ppp

Nmap done: 1 IP address (1 host up) scanned in 0.19 seconds

Currently there are three ports visible: 22, 80 and 3000 (visual studio code) Now turn on the firewall and see what happens.

bone$ sudo ufw enable
Command may disrupt existing ssh connections. Proceed with operation (y|n)? y
Firewall is active and enabled on system startup


host$ nmap 192.168.7.2
Starting Nmap 7.80 ( https://nmap.org ) at 2022-07-09 13:37 EDT
Nmap scan report for bone (192.168.7.2)
Host is up (0.014s latency).
Not shown: 999 closed ports
PORT     STATE SERVICE
22/tcp   open  ssh

Nmap done: 1 IP address (1 host up) scanned in 0.19 seconds

Only port 22 (ssh) is accessible now.

The firewall will remain on, even after a reboot. Disable it now if you don’t want it on.

bone$ sudo ufw disable
Firewall stopped and disabled on system startup

See the How-To Geek article for more examples.

Installing Additional Packages from the Debian Package Feed

Problem

You want to do more cool things with your BeagleBone by installing more programs.

Solution

The easiest way to install more software is to use +apt+:

bone$ sudo apt update
bone$ sudo apt install "name of software"

A sudo is necessary since you aren’t running as root. The first command downloads package lists from various repositories and updates them to get information on the newest versions of packages and their dependencies. (You need to run it only once a week or so.) The second command fetches the software and installs it and all packages it depends on.

How do you find out what software you can install? Try running this:

bone$ apt-cache pkgnames | sort > /tmp/list
bone$ wc /tmp/list
   67303   67303 1348342 /tmp/list
bone$ less /tmp/list

The first command lists all the packages that apt knows about and sorts them and stores them in /tmp/list. The second command shows why you want to put the list in a file. The wc command counts the number of lines, words, and characters in a file. In our case, there are over 67,000 packages from which we can choose! The less command displays the sorted list, one page at a time. Press the space bar to go to the next page. Press Q to quit.

Suppose that you would like to install an online dictionary (dict). Just run the following command:

bone$ sudo apt install dict

Now you can run dict.

Removing Packages Installed with apt

Problem

You’ve been playing around and installing all sorts of things with apt and now you want to clean things up a bit.

Solution

apt has a remove option, so you can run the following command:

bone$ sudo apt remove dict
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
libmaa3 librecode0 recode
Use 'apt autoremove' to remove them.
The following packages will be REMOVED:
dict
0 upgraded, 0 newly installed, 1 to remove and 27 not upgraded.
After this operation, 164 kB disk space will be freed.
Do you want to continue [Y/n]? y

Copying Files Between the Onboard Flash and the MicroSD Card

Problem

You want to move files between the onboard flash and the microSD card.

Solution

If you booted from the microSD card, run the following command:

bone$ df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs          7.2G  2.0G  4.9G  29% /
udev             10M     0   10M   0% /dev
tmpfs           100M  1.9M   98M   2% /run
/dev/mmcblk0p2  7.2G  2.0G  4.9G  29% /
tmpfs           249M     0  249M   0% /dev/shm
tmpfs           249M     0  249M   0% /sys/fs/cgroup
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           100M     0  100M   0% /run/user
bone$ ls /dev/mmcblk*
/dev/mmcblk0    /dev/mmcblk0p2  /dev/mmcblk1boot0  /dev/mmcblk1p1
/dev/mmcblk0p1  /dev/mmcblk1    /dev/mmcblk1boot1

The df command shows what partitions are already mounted. The line /dev/mmcblk0p2 7.2G 2.0G 4.9G 29% / shows that mmcblk0 partition p2 is mounted as /, the root file system. The general rule is that the media you’re booted from (either the onboard flash or the microSD card) will appear as mmcblk0. The second partition (p2) is the root of the file system.

The ls command shows what devices are available to mount. Because mmcblk0 is already mounted, /dev/mmcblk1p1 must be the other media that we need to mount. Run the following commands to mount it:

bone$ cd /mnt
bone$ sudo mkdir onboard
bone$ ls onboard
bone$ sudo mount /dev/mmcblk1p1 onboard/
bone$ ls onboard
bin   etc     lib         mnt           proc  sbin     sys  var
boot  home    lost+found  nfs-uEnv.txt  root  selinux  tmp
dev   ID.txt  media       opt           run   srv      usr

The cd command takes us to a place in the file system where files are commonly mounted. The mkdir command creates a new directory (onboard) to be a mount point. The ls command shows there is nothing in onboard. The mount command makes the contents of the onboard flash accessible. The next ls shows there now are files in onboard. These are the contents of the onboard flash, which can be copied to and from like any other file.

This same process should also work if you have booted from the onboard flash. When you are done with the onboard flash, you can unmount it by using this command:

bone$ sudo umount /mnt/onboard

Freeing Space on the Onboard Flash or MicroSD Card

Problem

You are starting to run out of room on your microSD card (or onboard flash) and have removed several packages you had previously installed (Removing Packages Installed with apt), but you still need to free up more space.

Solution

To free up space, you can remove preinstalled packages or discover big files to remove.

Removing preinstalled packages

You might not need a few things that come preinstalled in the Debian image, including such things as OpenCV, the Chromium web browser, and some documentation.

Note

The Chromium web browser is the open source version of Google’s Chrome web browser. Unless you are using the Bone as a desktop computer, you can probably remove it.

Here’s how you can remove these:

bone$ sudo apt remove bb-node-red-installer (171M)
bone$ sudo apt autoremove
bone$ sudo -rf /usr/share/doc               (116M)
bone$ sudo -rf /usr/share/man               (19M)

Discovering big files

The du (disk usage) command offers a quick way to discover big files:

bone$ sudo du -shx /*
12M  /bin
160M /boot
0    /dev
23M  /etc
835M /home
4.0K /ID.txt
591M /lib
16K  /lost+found
4.0K /media
8.0K /mnt
664M /opt
du: cannot access '/proc/1454/task/1454/fd/4': No such file or directory
du: cannot access '/proc/1454/task/1454/fdinfo/4': No such file or directory
du: cannot access '/proc/1454/fd/3': No such file or directory
du: cannot access '/proc/1454/fdinfo/3': No such file or directory
0    /proc
1.4M /root
1.4M /run
13M  /sbin
4.0K /srv
0    /sys
48K  /tmp
1.6G /usr
1.9G /var

If you booted from the microSD card, du lists the usage of the microSD. If you booted from the onboard flash, it lists the onboard flash usage.

The -s option summarizes the results rather than displaying every file. -h prints it in _human_ form–that is, using M and K postfixes rather than showing lots of digits. The /* specifies to run it on everything in the top-level directory. It looks like a couple of things disappeared while the command was running and thus produced some error messages.

Tip

For more help, try du –help.

The /var directory appears to be the biggest user of space at 1.9 GB. You can then run the following command to see what’s taking up the space in /var:

bone$ sudo du -sh /usr/*
4.0K /var/backups
76M  /var/cache
93M  /var/lib
4.0K /var/local
0    /var/lock
751M /var/log
4.0K /var/mail
4.0K /var/opt
0    /var/run
16K  /var/spool
987M /var/swap
28K  /var/tmp
16K  /var/www

A more interactive way to explore your disk usage is by installing ncdu (ncurses disk usage):

bone$ sudo apt install ncdu
bone$ ncdu /

After a moment, you’ll see the following:

ncdu 1.15.1 ~ Use the arrow keys to navigate, press ? for help
--- / ------------------------------------------------------------------
.   1.9 GiB [##########] /var
    1.5 GiB [########  ] /usr
  835.0 MiB [####      ] /home
  663.5 MiB [###       ] /opt
  590.9 MiB [###       ] /lib
  159.0 MiB [          ] /boot
.  22.8 MiB [          ] /etc
   12.5 MiB [          ] /sbin
   11.1 MiB [          ] /bin
.   1.4 MiB [          ] /run
.  40.0 KiB [          ] /tmp
!  16.0 KiB [          ] /lost+found
    8.0 KiB [          ] /mnt
e   4.0 KiB [          ] /srv
!   4.0 KiB [          ] /root
e   4.0 KiB [          ] /media
    4.0 KiB [          ]  ID.txt
.   0.0   B [          ] /sys
.   0.0   B [          ] /proc
    0.0   B [          ] /dev

Total disk usage:   5.6 GiB  Apparent size:   5.5 GiB  Items: 206148

ncdu is a character-based graphics interface to du. You can now use your arrow keys to navigate the file structure to discover where the big unused files are. Press ? for help.

Warning

Be careful not to press the D key, because it’s used to delete a file or directory.

Using C to Interact with the Physical World

Problem

You want to use C on the Bone to talk to the world.

Solution

The C solution isn’t as simple as the JavaScript or Python solution, but it does work and is much faster. The approach is the same, write to the /sys/class/gpio files.

Listing 38 Use C to blink an LED (blinkLED.c)
 1////////////////////////////////////////
 2//	blinkLED.c
 3//	Blinks the P9_14 pin
 4//	Wiring:
 5//	Setup:
 6//	See:
 7////////////////////////////////////////
 8#include <stdio.h>
 9#include <string.h>
10#include <unistd.h>
11#define MAXSTR 100
12// Look up P9.14 using gpioinfo | grep -e chip -e P9.14.  chip 1, line 18 maps to 50
13int main() {
14  FILE *fp;
15  char pin[] = "50";
16  char GPIOPATH[] = "/sys/class/gpio";
17  char path[MAXSTR] = "";
18
19  // Make sure pin is exported
20  snprintf(path, MAXSTR, "%s%s%s", GPIOPATH, "/gpio", pin);
21  if (!access(path, F_OK) == 0) {
22    snprintf(path, MAXSTR, "%s%s", GPIOPATH, "/export");
23    fp = fopen(path, "w");
24    fprintf(fp, "%s", pin);
25    fclose(fp);
26  }
27 
28  // Make it an output pin
29  snprintf(path, MAXSTR, "%s%s%s%s", GPIOPATH, "/gpio", pin, "/direction");
30  fp = fopen(path, "w");
31  fprintf(fp, "out");
32  fclose(fp);
33
34  // Blink every .25 sec
35  int state = 0;
36  snprintf(path, MAXSTR, "%s%s%s%s", GPIOPATH, "/gpio", pin, "/value");
37  fp = fopen(path, "w");
38  while (1) {
39    fseek(fp, 0, SEEK_SET);
40    if (state) {
41      fprintf(fp, "1");
42    } else {
43      fprintf(fp, "0");
44    }
45    state = ~state;
46    usleep(250000);   // sleep time in microseconds
47  }
48}

blinkLED.c

Here, as with JavaScript and Python, the gpio pins are referred to by the Linux gpio number. Mapping from header pin to internal GPIO number shows how the P8 and P9 Headers numbers map to the gpio number. For this example P9_14 is used, which the table shows in gpio 50.

cape headers digital

Fig. 222 Mapping from header pin to internal GPIO number

Compile and run the code:

bone$ gcc -o blinkLED blinkLED.c
bone$ ./blinkLED
^C

Hit ^C to stop the blinking.