You can issue the commands to manually configure the IPv6 stack manually.
ip -6 is your friend here, both for setting things up and checking things out.
The same config scripts that configure IPv4 configure IPv6. They will configure whatever is set, so you can't use them to configure IPv6 without restarting IPv4. Depending on what is configured you will start with any combination of IPv4 and IPv6.
You will likely find that IPv6 is already configured in link local mode. The following is an example
/etc/network/interfaces stanza. This is for a host getting the gateway from a
radv notification. The MTU is to handle a 4to6 or 4in6 tunnel to the Internet. However, if you are using a
radvd daemon most of your servers should configure themselves. You only need the stanza if you want to add the hosts to DNS. Your radvd will need one or two stanzas to setup it's interfaces.
iface eth0 inet6 static
I documented my IPv6 setup for OpenWRT, and the
radvd setup works for Ubuntu. Most of what I documented in IPv6 Part2 runs on Ubuntu.