Is it possible to run dhclient to get an IP on a second interface, after its already running in the first place? Say I run dhclient eth0 to get an IP. An hour later I decide to turn on my wireless for some reason, and I want to grab an IP... how do I go about doing it without releasing my dhclient or killing it? attempting to run dhclient eth1 at that point complains that its already running.

At home all I do is ifup eth1 and dhclient automagically gets an IP for eth1.

I'm guessing thats because you have an ifcfg-eth1 file right? I have one for my wired NIC because I use that the most. I don't have an ifcfg-eth1 because I connect to different wireless networks using varying authentication types (working on setting up xsupplicant to handle that right now) so no set config for that.

I notice if I issue an ifconfig eth0 up, it doesn't attempt to get an address, only if I run an ifup... do you know if a way to tell dhclient to get an IP for that interface if you don't have a cfg file for it? I tried making a generic config that was set "onboot=no" to see if that would satisfy it, so I'll test it shortly.

I don't believe I have an ifcfg-eth1 file. I'm running Debian and I think that file is RH specific. I guess I missed the wireless part too because mine's a desktop w/ two NICs, so no wireless. But eth1 is setup in my /etc/network/interfaces file (which maybe is equivalent to the ifcfg-eth1 file). Sorry, seems I'm pretty useless here.

Nope, you're right. You do have a config file for that interface. I made a dummy file for mine to see if it will work. I'm curious though if it can be made to work if there is no configuration file for that interface.