Connecting to the USB Console Port

This guide shows how to access the serial console which can be used for troubleshooting and diagnostics tasks as well as some basic configuration.

There are times when directly accessing the console is required. Perhaps GUI or SSH access has been locked out, or the password has been lost or forgotten.

Install the Driver

A Silicon Labs CP210x USB-to-UART Bridge driver is used to provide access to the console, which is exposed via the USB Mini-B (5-pin) port on the appliance.

If needed, install an appropriate Silicon Labs CP210x USB to UART Bridge driver on the workstation used to connect with the device.

There are drivers available for Windows available for download.

Note

The correct driver should install automatically for Windows 10 and above the first time the workstation is connected to the Netgate® appliance. It may take up to 3 minutes for the driver to install.

There are drivers available for macOS available for download.

For macOS, choose the CP210x VCP Mac download.

There are drivers available for Linux available for download.

Recent versions of many Linux distributions include this driver and will not require manual installation.

Note

If the device does not appear automatically, the driver module may need to be loaded manually, especially if the version of Linux being run is not recent. If the driver was provided with the Linux distribution, run sudo modprobe cp210x. If it had to be built manually, run insmod ./cp210x.ko assuming the module is in the current directory.

Recent versions of FreeBSD include this driver and will not require manual installation.

Connect a USB Cable

Next, locate an appropriate USB cable that has a USB Mini-B (5-pin) connector on one end and a regular USB Type A plug on the other end. These cables are commonly used with smaller USB peripherals such as GPS units, cameras, and so on.

Gently push the USB Mini-B (5-pin) plug end into the console port on the appliance and connect the USB Type A plug into an available USB port on the workstation.

Tip

Be certain to gently push in the USB Mini-B (5-pin) connector on the device side completely. With most cables there will be a tangible “click”, “snap”, or similar indication when the cable is fully engaged.

Apply Power to the Device

On some devices when using a USB serial console port the serial port will not appear on the client operating system until the device is plugged into a power source.

If the client OS does not see the serial device, connect the power cord to the device to allow it to start booting.

If the device appears without power, then better to wait until the terminal is open before connecting power so the client can view the entire boot output.

Locate the Console Port Device

The appropriate console port device that the workstation assigned as the serial port must be located before attempting to connect to the console.

Note

Even if the serial port was assigned in the BIOS, the workstation OS may remap it to a different COM Port.

To locate the device name on Windows, open Device Manager and expand the section for Ports (COM & LPT). Look for an entry with a title such as Silicon Labs CP210x USB to UART Bridge. If there is a label in the name that contains “COMX” where X is a decimal digit (e.g. COM3), that value is what would be used as the port in the terminal program.

assignment

The device associated with the system console is likely to show up as, or start with, /dev/cu.usbserial-<id>.

Run ls -l /dev/cu.* from a Terminal prompt to see a list of available USB serial devices and locate the appropriate one for the hardware. If there are multiple devices, the correct device is likely the one with the most recent timestamp or highest ID.

The device associated with the system console is likely to show up as /dev/ttyUSB0. Look for messages about the device attaching in the system log files or by running dmesg.

Note

If the device does not appear in /dev/, see the note above in the driver section about manually loading the Linux driver and then try again.

The device associated with the system console is likely to show up as /dev/cuaU0. Look for messages about the device attaching in the system log files or by running dmesg.

Note

If the serial device is not present, ensure the device has power and then check again.

Launch a Terminal Program

Use a terminal program to connect to the system console port. Some choices of terminal programs:

For Windows the best practice is to run PuTTY in Windows or SecureCRT. An example of how to configure PuTTY is below.

Warning

Do not use Hyperterminal.

For macOS the best practice is to run GNU screen, or cu. An example of how to configure GNU screen is below.

For Linux the best practices are to run GNU screen, PuTTY in Linux, minicom, or dterm. Examples of how to configure PuTTY and GNU screen are below.

For FreeBSD the best practice is to run GNU screen or cu. An example of how to configure GNU screen is below.

Client-Specific Examples

PuTTY in Windows

  • Open PuTTY and select Session under Category on the left hand side.

  • Set the Connection type to Serial

  • Set Serial line to the console port determined previously

  • Set the Speed to 115200 bits per second.

  • Click the Open button

PuTTY will then display the console.

../_images/putty1.png

An example of using PuTTY in Windows

PuTTY in Linux

  • Open PuTTY from a terminal by typing sudo putty

    Note

    The sudo command will prompt for the local workstation password of the current account.

  • Set the Connection type to Serial

  • Set Serial line to /dev/ttyUSB0

  • Set the Speed to 115200 bits per second

  • Click the Open button

PuTTY will then display the console.

../_images/putty-linux.jpg

An example of using PuTTY in Linux

GNU screen

In many cases screen may be invoked simply by using the proper command line, where <console-port> is the console port that was located above.

$ sudo screen <console-port> 115200

Note

The sudo command will prompt for the local workstation password of the current account.

If portions of the text are unreadable but appear to be properly formatted, the most likely culprit is a character encoding mismatch in the terminal. Adding the -U parameter to the screen command line arguments forces it to use UTF-8 for character encoding:

$ sudo screen -U <console-port> 115200

Terminal Settings

The settings to use within the terminal program are:

Speed

115200 baud, the speed of the BIOS

Data bits

8

Parity

None

Stop bits

1

Flow Control

Off or XON/OFF.

Warning

Hardware flow control (RTS/CTS) must be disabled.

What’s Next?

After connecting a terminal client, it may not immediately see any output. This could be because the device has already finished booting or it may be that the device is waiting for some other input.

If the device does not yet have power applied, plug it in and monitor the terminal output.

If the device is already powered on, try pressing Space. If there is still no output, press Enter. If the device was booted, it may redisplay the console menu or login prompt, or produce other output indicating its status.

From the console, a variety of things are possible, such as changing interface addresses. There is a full explanation of every console menu option in the pfSense software documentation.

Troubleshooting

Serial Device Missing

With a USB serial console there are a few reasons why the serial port may not be present in the client operating system, including:

No Power

Some models require power before the client can connect to the USB serial console.

USB Cable Not Plugged In

For USB consoles, the USB cable may not be fully engaged on both ends. Gently, but firmly, ensure the cable has a good connection on both sides.

Bad USB Cable

Some USB cables are not suitable for use as data cables. For example, some cables are only capable of delivering power for charging devices and not acting as data cables. Others may be of low quality or have poor or worn connectors.

The ideal cable to use is the one that came with the device. Failing that, ensure the cable is of the correct type and specifications, and try multiple cables.

Wrong Device

In some cases there may be multiple serial devices available. Ensure the one used by the serial client is the correct one. Some devices expose multiple ports, so using the incorrect port may lead to no output or unexpected output.

Hardware Failure

There could be a hardware failure preventing the serial console from working. Contact Netgate TAC for assistance.

No Serial Output

If there is no output at all, check the following items:

USB Cable Not Plugged In

For USB consoles, the USB cable may not be fully engaged on both ends. Gently, but firmly, ensure the cable has a good connection on both sides.

Wrong Device

In some cases there may be multiple serial devices available. Ensure the one used by the serial client is the correct one. Some devices expose multiple ports, so using the incorrect port may lead to no output or unexpected output.

Wrong Terminal Settings

Ensure the terminal program is configured for the correct speed. The default BIOS speed is 115200, and many other modern operating systems use that speed as well.

Some older operating systems or custom configurations may use slower speeds such as 9600 or 38400.

Device OS Serial Console Settings

Ensure the operating system is configured for the proper console (e.g. ttyS1 in Linux). Consult the various operating install guides on this site for further information.

PuTTY has issues with line drawing

PuTTY generally handles most cases OK but can have issues with line drawing characters on certain platforms.

These settings seem to work best (tested on Windows):

Window
Columns x Rows

80x24

Window > Appearance
Font

Courier New 10pt or Consolas 10pt

Window > Translation
Remote Character Set

Use font encoding or UTF-8

Handling of line drawing characters

Use font in both ANSI and OEM modes or Use Unicode line drawing code points

Window > Colours
Indicate bolded text by changing

The colour

Garbled Serial Output

If the serial output appears to be garbled, binary, or random characters check the following items:

Terminal Speed

Ensure the terminal program is configured for the correct speed. (See No Serial Output)

Character Encoding

Ensure the terminal program is configured for the proper character encoding, such as UTF-8 or Latin-1, depending on the operating system. (See GNU Screen)

Serial Output Stops After the BIOS

If serial output is shown for the BIOS but stops afterward, check the following items:

Terminal Speed

Ensure the terminal program is configured for the correct speed for the installed operating system. (See No Serial Output)

Device OS Serial Console Settings

Ensure the installed operating system is configured to activate the serial console and that it is configured for the proper console (e.g. ttyS1 in Linux). Consult the various operating install guides on this site for further information.

Bootable Media

If booting from a USB flash drive, ensure that the drive was written correctly and contains a bootable operating system image.