Strictly speaking, Cobalt does not use TFTP but NFS to boot. You need to
install an NFS server and put the installer files in
/nfsroot. When you boot your Cobalt, you have to
press the left and the right cursor buttons at the same time and the
machine will boot via the network from NFS. It will then display several
options on the display. There are the following two installation methods:
Via SSH (default): In this case, the installer will configure the network via DHCP and start an SSH server. It will then display a random password and other login information (such as the IP address) on the Cobalt LCD. When you connect to the machine with an SSH client you can start with the installation.
Via serial console: Using a null modem cable, you can connect to the serial port of your Cobalt machine (using 115200 bps) and perform the installation this way.