/etc/network/interfaces

# The primary network interface
auto eth0
iface eth0 inet static
        address 192.168.1.11
        netmask 255.255.255.0
        network 192.168.1.0
        gateway 192.168.1.1

Don't forget to disable the DHCP server in the router!

sudo /etc/init.d/networking restart

To remove the password for the main admin when entering superuser mode, do the following:

visudo
add line: <username> ALL=(ALL) NOPASSWD: ALL

Before starting the new install, do the following:

• make a copy of /etc and /home/username
• install ubuntu
• copy /etc/lvm from backup
• lvm> vgcfgrestore vg
• copy /etc/fstab from backup

If you want to start with fresh settings for your username, additionally do the following:

• mount /home which resides on a lv to a different mount-point (e.g. /backup) and rename your previous /home/username
• copy /home/username to /backup
• umount /backup and mount /home, /srv, /backup (my lv created during the previous installation)

Finally, you need to change the ownership of your previous username:

chown -R username:users /home/username 

apt-get remove network-manager network-manager-gnome

Changing network cards or the motherboard requires to update the MAC adresses:

vim /etc/udev/rules.d/70-persistent-net-rules