I'm not an advanced Ubuntu user so please be patient with me.

I've installed Ubuntu 14.04.2 LTS, signed my computer to a Windows domain (using nis) and was able to login with my domain user.
I've also added my user to the sudoers group.

Now I have two issues:

1. When my computer is not in the network, I can't login with my domain user
2. Every time I reboot Ubuntu, I need to type my username again (this is a minor issue)

I've searched for a solution all over the place but was unable to find it.