[debian] /etc/network/interfaces

こんな感じ
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# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp


iface eth1 inet dhcp
wireless_mode managed


auto eth2
iface eth2 inet dhcp
wireless_mode managed
wireless-essid XXXXXXXXXX
wireless-key s:XXXXXXXXXX