For your account only edit:

sudo vi /home/<username>/.bashrc

sudo vi /etc/profile

export http_proxy=http://10.0.0.1:8080
export https_proxy=https://10.0.0.1:8080

source /home/<username>/.bashrc

or

source /etc/profile

Open apt.conf

vi /etc/apt/apt.conf

Set proxy

Acquire::http::Proxy "http://127.0.0.1:8080";
Acquire::https::Proxy "https://127.0.0.1:8080";

Open wgetrc

vi ~/.wgetrc

Set proxy

use_proxy=on
http_proxy=127.0.0.1:8080
https_proxy=127.0.0.1:8080

OR

wget <URL> -e use_proxy=on -e http_proxy=127.0.0.1:8080

Edit /etc/network/interfaces:

sudo vi /etc/network/interfaces

auto eth0
iface eth0 inet static
        address 10.0.0.2
        netmask 255.0.0.0
        network 10.0.0.0
        broadcast 10.0.0.255
        gateway 10.0.0.1
        dns-nameservers 10.0.0.1

/etc/init.d/networking restart

Edit /etc/hosts

sudo vi /etc/hosts

127.0.0.1       localhost.localdomain localhost
127.0.1.1       ubuntu.lunetikk.de ubuntu
10.0.0.2        ubuntu.lunetikk.de ubuntu

sudo vi /etc/hostname

hostname –F /etc/hostname

 dpkg-reconfigure resolvconf 

# ifdown eth0 && ifup eth0
/etc/resolvconf/update-libc.d/sendmail: 7: .: Can't open /usr/share/sendmail/dynamic
run-parts: /etc/resolvconf/update-libc.d/sendmail exited with return code 2
run-parts: /etc/resolvconf/update.d/libc exited with return code 1
/etc/resolvconf/update-libc.d/sendmail: 7: .: Can't open /usr/share/sendmail/dynamic
run-parts: /etc/resolvconf/update-libc.d/sendmail exited with return code 2
run-parts: /etc/resolvconf/update.d/libc exited with return code 1
/etc/network/if-up.d/sendmail: 44: .: Can't open /usr/share/sendmail/dynamic
run-parts: /etc/network/if-up.d/sendmail exited with return code 2

This should fix it:

 apt-get --purge remove sendmail sendmail-base sendmail-bin