EBC Exercise 02 Out-of-the-Box, Bone

Embedded Linux Class by Mark A. Yoder

3.8 Kernel

These instructions are for the 3.8 and newer kernels. EBC Exercise 02 Out-of-the-Box, Bone 3.2 Kernel has instructions for the 3.2 kernel.

Local Internet Connection, Cloud 9

One of the slickest features of the Bone is its ability to access the Internet through the USB (tether) connection. Plug a USB cable into your bone and plug the other end into your host computer and wait for the Bone to boot up. Once the lights settle down to a heartbeat pattern point a browser on your host computer to 192.168.7.2. Here you will see the Cloud 9 IDE (integrated development environment). This is being served up by the Bone over a local internet connection. Go and explore it.

Internet Connection to the Outside World

Once the Bone can connect to the host, the host can be used for forward requests from the Bone to the Internet. Follow the instructions below to set up your host and Bone so the bone can access the internet through your host.

Linux

See your networks with ip a

Run:

host$ 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: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:8c:63:ea brd ff:ff:ff:ff:ff:ff
    inet 172.16.105.242/24 brd 172.16.105.255 scope global dynamic noprefixroute ens33
       valid_lft 6327sec preferred_lft 6327sec
    inet6 2605:a000:1c02:ec:5936:3599:8ce1:c3cb/64 scope global temporary dynamic 
       valid_lft 86396sec preferred_lft 14396sec
    inet6 2605:a000:1c02:ec:a067:7cb0:fd3e:7d13/64 scope global dynamic mngtmpaddr noprefixroute 
       valid_lft 86396sec preferred_lft 14396sec
    inet6 fe80::9d5f:d5d0:6460:d5cd/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: enx40bd32e49bc1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 40:bd:32:e4:9b:c1 brd ff:ff:ff:ff:ff:ff
    inet 192.168.6.1/30 brd 192.168.6.3 scope global dynamic noprefixroute enx40bd32e49bc1
       valid_lft 103sec preferred_lft 103sec
    inet6 fe80::6f61:86ba:523e:c1d5/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
4: enx40bd32e49bbe: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 1000
    link/ether 40:bd:32:e4:9b:be brd ff:ff:ff:ff:ff:ff
    inet 192.168.7.1/30 brd 192.168.7.3 scope global dynamic noprefixroute enx40bd32e49bbe
       valid_lft 103sec preferred_lft 103sec
    inet6 fe80::9603:1b84:ebd5:7c9c/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

ssh and changing the password

You'll see two new networks have appeared, enx40bd32e49bc1 and enx40bd32e49bbe in my case. The IP address of your host is 192.168.7.1. There's a good chance the Bone is at 192.168.7.2. Try connecting to it. The default password is temppwd.

host$ ssh debian@192.168.7.2
bone$ 

You are now logged into the Bone through the network. This is much faster than the serial port (.115M vs. 100M) and supports many interesting network operations.

Take a look around. What do you find?

Since everyone knows the default password, change it to something else.

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

The only problem is, the Beagle doesn't know how to access the Internet through the host. Get back to the host computer:

bone$ exit

Setting up shortcuts to make life easier

We'll be ssh'ing from the host to the bone often, here are some shortcuts I use so instead of typing ssh debian@192.168.7.2 and a password every time, I can enter ssh bone and no password.

First edit /etc/hosts and add a couple of lines.

host$ sudo nano /etc/hosts

You may use whatever editor you want. I suggest nano since it's easy to figure out. Add the following to the end of /etc/hosts and quit the editor.

192.168.7.2     bone
192.168.8.1     bone2

Now you can connect with

host$ ssh debian@bone

Let's make it so you don't have to enter debian. On your host computer, put the following in ~/.ssh/config

Host bone
  User debian
  UserKnownHostsFile /dev/null
  StrictHostKeyChecking no

Host bone2
  User debian
  UserKnownHostsFile /dev/null
  StrictHostKeyChecking no

These say that whenever you login to bone or bone2, login as debian. Now you can enter.

host$ ssh bone

One last thing, let's make it so you don't have to add a password. Back to your host.

host$ ssh-keygen

Accept all the defaults and then

host$ ssh-copy-id bone

Now all you have to enter is

host$ ssh bone

and no password is required. If you, especially virtual machine users, get an error says "sign_and_send_pubkey: signing failed: agent refused operation", you can solve this by entering

host$ ssh-add

which adds the private key identities to the authentication agent. Then you should be able to

host$ ssh bone

without problems.

Setting up a root login

By default the image we are running doesn't allow a root login. You can also sudo from debian, but sometimes it's nice to login as root. Here's how to setup root so you can login from your host without a password.

host$ ssh bone
bone$ sudo bash
root@bone# nano /etc/ssh/sshd_config

Search for the line

#PermitRootLogin prohibit-password

and change it to

PermitRootLogin yes

(The # symbol indicates a comment and must be removed in order for the setting to take effect.)

Save the file and quit the editor. Restart ssh so it will reread the file.

root@bone# systemctl restart sshd

And assign a password to root.

root@bone# passwd

Now open another window on your host computer and enter:

host$ ssh-copy-id root@bone

and enter the root password. Test it with:

host$ ssh root@bone

You should be connected without a password. Now go back to the Bone and turn off the root password access.

root@bone# nano /etc/ssh/sshd_config

Restore the line:

#PermitRootLogin prohibit-password

and restart sshd.

root@bone# systemctl restart sshd
root@bone# exit
bone$ exit

You should now be able to got back to your host computer and login as root on the bone without a password.

host$ ssh root@bone

You have access to your bone without passwords only from you host computer. Try it from another computer and see what happens.

Set Up Git

We need to run some files that are in the class git repository. We'll learn more about using git later. Here I'll just show you how to get the files. Here we are installing these files on your host computer, later we'll install them on your Beagle.

On my host computer I had to run

host$ sudo apt install git

Get the Files

It only takes one command to pull down all the files.

host$ git clone https://github.com/MarkAYoder/BeagleBoard-exercises.git exercises --depth=1

(The whole repo is some 700M. Using --depth=1 you only get the recent history and it only takes 200M.)

This will take a while since it's getting all the course files, including pdf files of the course PowerPoint.

Running ipMasquerade.sh

Now that the files are installed, run:

host$ cd exercises/setup
host$ ./ipMasquerade.sh ens33

Plug in for ens33 whatever is returned when you run ip a. This will give you instructions on how to set up your host. Note: If you are using a wireless connection you should use

host$ ./ipMasquerade.sh wlp16s0

where wlp16s0 is what is returned by ip a for your wireless connection on your host.

Once ./ipMasquerade.sh has been run you can:

host$ ./firstssh.sh

Now you should have network access on the Bone.

bone$ ping -c2 google.com

You should see Google responding.

Congratulations! Your Beagle is now on the network through your host computer.

You will have to run ipMasquerade.sh only after rebooting your host computer and run firstssh.sh after rebooting your bone. Once firstssh has be run you should ssh from your host with the standard ssh command.

Troubleshooting

Unknown Host

If you get an unknown host response when attempting to ping google.com, and you are off campus, try pinging the Google DNS by IP address. Run:

bone$ ping 8.8.8.8

If you are on campus, run:

bone$ ping 137.112.5.28

If you now see responses by pinging a specific IP, it is possible that a firewall on your host computer is blocking the Beagle's access to the DNS when attempting to ping by domain name. On Ubuntu/Mint, run:

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

You should get a response, such as above, that the firewall will be disabled upon next startup. After saving anything important, restart your host through the start menu or run:

host$ reboot

Repeat this exercise and attempt to ping Google by domain name again. If you now receive responses, then the firewall was indeed the issue. Otherwise, the internet is your friend. Use your host computer to try and find a solution. Feel free to add solutions here when you find them

NetworkManager Issues

If you continue to have problems with firstssh.sh and receive errors regarding the network manager command line tool (nmcli) such as:

mv: cannot stat '/etc/resolv.conf'

or

nmcli failed, trying older 'list' instead of 'show'
nmncli failed again, giving up. . .

then you may have success with the following solution.

Access your bone with ssh bone and check to see which network interface is tethered to your host. It should be usb0, already assigned the ip address of 192.168.7.2. If so, simply enter the following in the command line:

bone$ route add default gw 192.168.7.1

Now return to your host machine and check what your internet facing interface is. It should be some eno interface for a wired connection or wlp interface for wireless. Your Bone should be on one of the usb ports, starting with enx and showing an ip address for your host machine of 192.168.7.1. The example commands below will use wlp in place of the internet facing interface and enx in place of the Bone interface.

host$ iptables --table nat --append POSTROUTING --out-interface wlp -j MASQUERADE
host$ iptables --append FORWARD --in-interface enx -j ACCEPT
host$ echo 1 > /proc/sys/net/ipv4/ip_forward

You should now ssh into your Bone and see if the routing change has worked. These commands are essentially what the ipMasquerade.sh and firstssh.sh scripts already do, but I started to encounter problems with them and had more success performing the operations manually.

OS X

I haven't checked these instructions this year. Please report your results and update if needed.

1. go to System Preferences and select Network
2. You should see RNDIS/...Gadget. This is the network connection to the Beagle. Select it
3. Wait for the IP address 192.168.7.1 to appear
4. Click Show All and select Sharing
5. Select Internet Sharing
6. Select RNDIS/Ethernet Gadget

In a terminal window connect to the serial port

host$ screen /dev/ttyusb*B 115200
bone$ udhcpc -i usb0
bone$ ping google.com

This is all nicely shown here in this silent YouTube movie.

Congratulations, you now have a connection from your BeagleBone to the Internet.

Windows 7

I haven't checked these either. Please report results and update if needed.

There are several ways of running ssh on Windows 7. Below are a couple of tools that you can use.

Environment Setup

You can either run ssh from a bash terminal (i.e. C:\Program Files\Git\Git Bash or C:\cygwin\Cygwin.bat), or you can add the bin directories to your path and run from the Windows command prompt (i.e. add C:\Program Files\Git\bin or C:\cygwin\bin to your path).

Note: Be careful adding multiple bin directories to your path

First time setup

1. Run regedit
2. Navigate to Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Tcpip\Parameters
3. Change IPEnableRouter from 0 to 1
4. Close regedit
5. Run services
6. Make sure the following are set to Automatic and are started
   1. Routing and Remote Access
   2. Internet Connection Sharing (ICS)

Connecting to the Internet

After ejecting

1. Navigate to Control Panel\Network and Internet\Network and Sharing Center\Change adapter settings
2. Right click your wired/wireless internet connection and go to Properties
3. Go to the Sharing tab
4. Check the box to Allow other network users to connect through this computer's Internet connection
5. Select your bone's local area connection for the Home networking connection (if you cannot choose the local area connection, turn your internet connection sharing off and then back on)
6. Return to Change adapter settings
7. Right click your Bone's internet connection and go to Properties
8. Select Internet Protocol Version 4 (TCP/IPv4) and choose Properties
9. Choose Obtain an IP address automatically and Obtain DNS server address automatically

Open a command prompt or bash terminal and run the following:

host$ ping 192.168.7.2

If this ping times out then disable and re-enable your bone's local area connection and try again. Once it works run the following:

host$ ssh root@192.168.7.2

Login as root and run the following:

bone$ echo "nameserver 8.8.8.8" > /etc/resolv.conf
bone$ echo "nameserver 8.8.8.4" >> /etc/resolv.conf
bone$ /sbin/route add default gw 192.168.7.1
bone$ ping google.com

If 'ping:unknown host google.com' occurs, run this instead:

bone$ echo "nameserver 137.112.4.196" > /etc/resolv.conf
bone$ /sbin/route add default gw 192.168.7.1
bone$ ping google.com

Congratulations, you now have a connection from your BeagleBone through your Linux host to the Internet.

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Embedded Linux Class by Mark A. Yoder