ubuntu apt-get problem

# sudo cd /etc/apt
# sudo mv sources.list sources.list.ok
# sudo echo <<EOF
deb mirror://mirrors.ubuntu.com/mirrors.txt xenial main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt xenial-updates main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt xenial-backports main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt xenial-security main restricted universe multiverse
EOF > sources.list
# sudo apt-get clean
# sudo apt-get update