I hope this helps, at least with the DHCP part.
We use RH Linux and the DHCP leases (if that is what you are referring to) are stored in /var/lib/dhcp directory. The leases will show what computer (IP address / computer name) has registered via the DHCP on your DHCP Server.
If the direcory sturcture is different on your flavor of LINUX, you may try to use the locate command (if it is installed) to search for leases. Usage for me is
this found the dhcp leases file(s). You may also try this with
and it will show you all files named dhcp.
I hope this provides some assistance.
Have a good day.