Problems with ip addresses using dhcpd and tftpd

Hi there, I'm running a dhcpd to give an installing client an IP and to say it where the tftp is. Every client has a fixed address. My problem is, that, every time the client starts up, he gets an IP. Surely he should do this, but if it reboots after an installation... he installs again. That's not fine ;-) Do anyone know how to tell the dhcpd to only use an IP once? Next problem is, that I want to read out the overgiven IP address by the dhcpd. But if I do an `ifconfig' on client side, eth0 has no IP. Also I want to reuse the hostname statically, but there is none. Any hints? Thanks in advance, Markus