Remote Access for RDK S100¶

After flashing the system image, you can perform most daily development tasks from your computer. A remote terminal lets you edit code, transfer files, run programs, and inspect logs without keeping a monitor, keyboard, and mouse connected to the board.

This lesson first uses the J16 debug serial port to access the system, then configures a wired connection through eth1, and finally logs in over SSH. The serial console does not depend on the network, so it is useful for initial setup and troubleshooting. SSH requires a working network connection and is better suited to daily development.

Prerequisites¶

An RDK S100 that has been flashed and boots successfully
A USB Type-C cable that supports data transfer
An Ethernet cable
A Windows computer
MobaXterm, PuTTY, or another serial terminal application
The CH340 serial driver

RDK images normally provide the following default accounts. The credentials may vary with the image version and source, so also check the release notes for your image.

Privilege	Username	Password
Standard user	`sunrise`	`sunrise`
Superuser	`root`	`root`

This lesson uses root to inspect the system through the serial console and sunrise for daily work over SSH.

Connect to the J16 debug serial port¶

The USB Type-C J16 port on the RDK S100 supports system flashing as well as Main-domain and MCU-domain debugging. Two onboard CH340 chips convert the Main-domain and MCU-domain debug serial ports into USB serial devices. To access Ubuntu in this lesson, select the Main-domain channel that displays the Linux boot log.

In this procedure, J16 is used as a debug serial port. It cannot be configured with an IP address like an Ethernet interface.

Connect and identify the port¶

Connect the computer to the board's J16 port with the Type-C data cable.
Open Windows Device Manager and expand the list of ports.
Confirm that a new CH340 or CH341 serial device appears.
Note the newly assigned COM port number.

It is normal for more than one serial device to appear. If the selected port does not show Linux output, try the other newly added port.

If no new COM port appears in Device Manager, confirm that the cable supports data transfer, then check the CH340 driver.

Configure the serial terminal¶

The following example uses MobaXterm. Create a Serial session and apply these settings.

Setting	Value
Serial port	The COM port shown in Device Manager
Baud rate	`921600`
Data bits	`8`
Parity	`None`
Stop bits	`1`
Flow control	`None`

Open the session and press Enter once. The terminal should display a login prompt or a Linux shell.

At the login prompt, enter root as both the username and password. The terminal does not display asterisks or other characters while you type the password. Press Enter when finished.

After logging in, check the address assigned to eth1.

ip -br addr show eth1

With the default configuration, the output should include 192.168.127.10/24. You can also list all network interfaces with the following command.

ifconfig -a

Connect the eth1 wired network¶

The RDK S100 has two Gigabit Ethernet ports. Their default configurations are different. This lesson uses eth1 because it has a predefined static address.

Physical port	Linux interface	Default configuration	Default address
U43	eth0	DHCP or manual configuration	None
U45	eth1	Static address	`192.168.127.10`

The outer RJ45 port on the board corresponds to eth1. Connect the Ethernet cable to this port and connect the other end directly to the computer.

Location of the RDK S100 eth1 port

The default eth1 network settings are shown below.

Setting	Value
IP address	`192.168.127.10`
Subnet mask	`255.255.255.0`
Gateway	`192.168.127.1`

Configure a static address on the computer¶

Open the Windows Network Connections page.
Find the Ethernet adapter connected to the board.
Open the adapter properties.
Double-click Internet Protocol Version 4.
Select manual address configuration and enter the following values.

Setting	Value
Computer IP address	`192.168.127.100`
Subnet mask	`255.255.255.0`
Default gateway	`192.168.127.1`

The computer and board must be on the same subnet and must use different IP addresses. Do not assign the board's 192.168.127.10 address to the computer.

Verify network connectivity¶

Open PowerShell and run the following command.

ping 192.168.127.10

Replies from 192.168.127.10 confirm that the computer can reach the board. Complete this check successfully before attempting an SSH login.

If the request times out, verify that the cable is connected to eth1, the computer uses 192.168.127.100, the subnet mask is correct, and Windows Firewall is not blocking the current network.

Log in over SSH¶

After the ping test succeeds, run the following command in PowerShell.

ssh sunrise@192.168.127.10

You can also create an SSH session in MobaXterm with 192.168.127.10 as the remote host and sunrise as the username.

On the first connection, SSH asks you to confirm the board's host key. Enter yes, press Enter, and then enter the password sunrise. No characters appear while you type the password.

A prompt similar to the following confirms that the SSH login succeeded.

sunrise@ubuntu:~$

Run these commands to verify the current user and network interface.

whoami
hostname
ip -br addr show eth1

whoami should print sunrise, and the eth1 output should include 192.168.127.10/24.

Transfer files¶

After SSH is working, use SCP on the computer to copy files to the board. The following example sends hello.txt from the current directory to the standard user's home directory.

scp .\hello.txt sunrise@192.168.127.10:/home/sunrise/

Enter the password sunrise. After the transfer finishes, check the file from the SSH terminal.

ls -l /home/sunrise/hello.txt

Add the -r option to copy an entire directory.

scp -r .\demo sunrise@192.168.127.10:/home/sunrise/

Troubleshooting¶

The computer does not detect a COM port¶

Confirm that the Type-C cable supports data transfer and reinstall the CH340 driver. You can also try another USB port or cable to rule out a hardware problem.

The serial output is garbled¶

Confirm a baud rate of 921600, 8 data bits, no parity, 1 stop bit, and no flow control.

The serial terminal shows no output¶

Confirm that you selected the Main-domain debug channel. Open the serial session before restarting the board so that you can capture the complete Linux boot log.

The ping test fails¶

Confirm that the cable is connected to the outer eth1 port. Then verify that the computer and board are both on the 192.168.127.0/24 subnet and do not use the same IP address.

SSH reports Connection refused¶

Log in through the serial console and check the SSH service.

systemctl status ssh

If the service is not running, try starting it.

systemctl start ssh

PowerShell cannot find the ssh command¶

Install the OpenSSH Client from Windows Optional Features, or create an SSH session in MobaXterm. The remote address and login credentials are the same with either tool.

SSH reports Permission denied¶

Use sunrise as both the username and password for a normal SSH login. Check the capitalization of the username and remember that the password has no visible feedback while you type it.

The host identity warning appears after reflashing¶

Reflashing can change the board's SSH host key. After confirming that the target is still your own board, remove the old record from the computer.

ssh-keygen -R 192.168.127.10

Then run the SSH login command again.