What additional hard and software do I need to run and manage a Soekris box

From Soekris Info Wiki

What additional hard- and software do I need to run and manage a Soekris box?

You will need a 12-20V power supply, a null-modem cable and, of course, a PC or other computer with a serial port (or else an USB adapter with an appropriate driver). Apart from that, you'll need a program for serial communication, like cu or minicom. Null-modem cables are readily available these days thanks to the STB. If you need to make one yourself, an excellent docs is found here.

Note that in the Open Source world, support for RS232 over USB varies, and does not appear to have top priority.

To perform the initial installation of your OS, there are two common methods. The first is to perform a network install by PXE booting the machine. Refer to your OS's documentation for specifics on this procedure. This will typically require at least a DHCP server that you can configure and a TFTP server to load the installation image. The second is to prepare a hard drive or compact flash drive on another computer. This will require appropriate adapters for your choice of media. Please note that USB->Compact Flash adapters sometimes encounter geometry issues, the best way to avoid this is to do a PXE install on the Soekris itself.