Here’s a quick HOWTO for updating a Soekris net4801 BIOS using cu(1) and lsx(1) from comms/lrzsz under FreeBSD.

First, establish contact to the BIOS using something like ‘cu -l /dev/ttyU0 -s 19200′ adjusted to fit the device node and speed used in your setup. Then follow these steps:

1. Press Ctrl+P to enter the Soekris BIOS monitor
2. Type download -
3. Press ~C
4. Type lsx /path/to/b4801_131.bin

If the XMODEM transfer was successful, continue with the following steps:

1. Type flashupdate
2. Type reboot
3. Press ~. to exit cu(1)

That’s it! The BIOS should now be updated :)