Run Quectel's Connection Manager as a systemd service on Ubuntu

I found myself in possession of a modem by Quectel (https://www.quectel.com) to hook up to a Raspberry Pi running Ubuntu 20.04. I wanted to auto run Quectel's connection manager executable quectel-CM on system start up but found limited information available online from Quectel. So I had to roll up my sleeves and make my own systemd service for that purpose.

This post outlines the steps I took:

Download and compile the quectel-CM executable

1. Using an Internet browser, download the latest Quectel LTE, 5G Linux USB driver, e.g. Quectel_LTE5G_Linux_USB_Driver_V1.0.zip from https://www.quectel.com/download-zone.
    
2.  Extract QConnectManager_Linux_V1.0.zip into a folder e.g. /home/ubuntu/Downloads/quectel-CM/.
   
   
3. In a Terminal, change directory to the extracted folder.
   
   $ cd ~/Downloads/quectel-CM/
   
   
4. Use the make command to compile the connection manager executable.
   
   $ make
   
   The quectel-CM executable is compiled.
   
   

Place the quectel-CM exe to the run time directory

1. In a Terminal, type in the following commands to change directory to the extracted directory.
   
   $ cd /home/ubuntu/Downloads/quectel-CM/
   
   
2. Copy the executable to /usr/local/bin/.
   
   $ sudo cp quectel-CM /usr/local/bin
   
   

Create a systemd service file

1.  In the directory /etc/systemd/system, use a text editor to create a service file e.g. quectelcm.service.
   
   $ sudo vi /etc/systemd/system/quectelcm.service
   
   
2. Type in the following lines, save and exit the file:
   

   [Unit]
   Description=Systemd service for running Quectel's Connection Manager quectel-CM executable
   
   [Service]
   ExecStart=/usr/local/bin/quectel-CM 
   Restart=always
   RestartSec=5
   
   [Install]
   WantedBy=multi-user.target
   

   
   
3. Give the service file the following executable permission:
   
   $ sudo chmod 664 /etc/systemd/system/quectelcm.service
   

 Create the service

1. In the Terminal, type in the following commands:
   
   $ sudo systemctl daemon-reload
   $ sudo systemctl enable quectelcm
   
   The quectelcm service is created.
   

 

Running and monitoring the service

1. You can either reboot the Raspberry Pi or type in the following command to start the service in a Terminal.
   
   $ sudo systemctl start quectelcm
   
   
2. To monitor the quectelcm service, use the journalctl command:
   
   $ journalctl -u quectelcm -f
   
   
   

Note: In order for quectel-CM to request and set the machine's network address, the software prerequisites net-tools and udhcpc must be installed on the Raspberry Pi.

Configure an Ubuntu VirtualBox guest instance for ssh access from the host OS

I use VirtualBox to run guest OS such as Ubuntu 18.04 virtual machines for trying out stuff and experiments to prevent messing up my host operating system, e.g. Ubuntu. For convenience, the guest Ubuntu OS running in the VirtualBox can be accessed remotely from the host OS by creating a network adapter that bridges between the host and the guest. This post describes the configuration needed to allow the host OS to connect to the guest OS remotely through a secured shell (ssh).

The following steps assume an Ubuntu virtual machine has been created in VirtualBox and shutdown.

Create a bridge network adapter

1. Run VirtualBox.
   
   The VirtualBox Manager is displayed.
   
   
2. Select the Ubuntu virtual machine e.g. vm1. Click Settings.
   
   The Settings appear.
   
   
3. Select Network.
   
   
   
4. Select the Adapter 2 tab. Toggle on the Enable Network Adapter field.
   
   
   
5. Choose Bridged Adapter in the Attached to field.
   
6. In the Name field, choose the network you want the virtual machine to join, e.g. wlp3s0. Click OK.
   
   The bridged network adapter is created in the virtual machine.

 Identify the virtual machine's IP address on the bridged network

1. In VirtualBox, run the guest virtual machine, e.g. vm1.
   
2. Log in to the guest OS. Open up a Terminal.
   
3. Type in the ifconfig command at the prompt:
   
   A list of network adapters and related information is displayed.
   
   
   
4. Note down the virtual machine's ip address, e.g. 192.168.0.189.

Install SSH server
If the SSH server is not installed in the guest Ubuntu OS, then do the following steps.

1. Open a Terminal.
   
2. At the prompt, type in the command:
   
   $ sudo apt-get install openssh-server
   
3. At the prompt, type in the command to enable the ssh service.
   
   $ sudo systemctl enable ssh
   
4. Start the ssh service by entering the following command.
   
   $ sudo systemctl start ssh
   

Remote access to the guest virtual machine
Now the virtual machine can be accessed from the host operating system. With the virtual machine running, the following commands can be used to access the guest OS.

1. Open up a Terminal. Type in the following command:
   
   $ ssh remote_user@192.168.0.189
   
   Note: where remote_user is the login name for the guest OS and 192.168.0.189 is the IP address of the virtual machine on the host's network.
   

Replaying network packets captured in a PCAP file

Some devices broadcast GPS positions over the network and saved into a PCAP file. Incidentally, PCAP stands for Packet CAPture. I got hold of some PCAP files and tried to use the Linux tcpreplay command to playback the captured network packets over the network.

The tcpreplay command input arguments require to specify the network interface and it conveniently advertises an option --listnics to list all the network interfaces on your machine. An example usage is displayed in  the screenshot below.

$ sudo tcpreplay --listnics


However, using any of the listed interfaces will result in an error when attempting to playback a pcap file, as shown below.

$ sudo tcpreplay --intf1 bluetooth0 *.pcap



After some research, I found the ip command with the link option that lists the network interfaces correctly.

$ ip link



Now plugging in the correct interface name into the tcpreplay command, my network packets are successfully replayed and broadcasted.

$ sudo tcpreplay --intf1 enp0s25 *.pcap