Hey guys, I try to do my homework and messed around with a few linux based platforms. Well I am hooked on Kali at the moment and just need a few straight answers to a few straight questions.

1. When running Kali live from a usb boot, i run 'apt-get update && apt-get upgrade' to update my files. Now i havent manually set up a partition yet, and wondering if it will save onto the usb (16GB) ....or will i need to run persistence in order for it to save (if that is even possible) ?? Thanks

2. Ettercap is killing me. I have configured the etter.conf file, removed the #, changed the ec_uid/gid to 0, and specificed <iface> to <eth0> ... and the ports to -dport 80 -j REDIRECT --to-port 10000.
But when i try the ettercap GUI, and set the network interface to 'eth0' ..when i start the unifed sniffing for a host scan all i get is ;

Randomizing -1 hosts for scanning....
Scanning the whole netmask for -1 hosts...
0 hosts added to the hosts list.

Configuring the ports and ip addresses is proving abit troublesome for me. Any straight forward instructions will be praised.
I have spent so many countless hours trying to get the network correct, ha please anyone...

3. Also could anyone recommend - the best way to obtain ip adresses. Nmap Arping seem both to be abit flawed ?
- the best way to scan a network/subnet? Any recommendations would be great

Thanks guys i really appreciate it.