1. Modify the source list sudo gedit /etc/apt/sources.list source is below 163, available tried
deb http://mirrors.163.com/ubuntu/ precise main restricted deb-src http://mirrors.163.com/ubuntu/ precise main restricted deb http://mirrors.163.com/ubuntu/ precise-updates main restricted deb-src http://mirrors.163.com/ubuntu/ precise-updates main restricted deb http://mirrors.163.com/ubuntu/ precise universe deb-src http://mirrors.163.com/ubuntu/ precise universe deb http://mirrors.163.com/ubuntu/ precise-updates universe deb-src http://mirrors.163.com/ubuntu/ precise-updates universe deb http://mirrors.163.com/ubuntu/ precise multiverse deb-src http://mirrors.163.com/ubuntu/ precise multiverse deb http://mirrors.163.com/ubuntu/ precise-updates multiverse deb-src http://mirrors.163.com/ubuntu/ precise-updates multiverse deb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ precise-security main restricted deb-src http://mirrors.163.com/ubuntu/ precise-security main restricted deb http://mirrors.163.com/ubuntu/ precise-security universe deb-src http://mirrors.163.com/ubuntu/ precise-security universe deb http://mirrors.163.com/ubuntu/ precise-security multiverse deb-src http://mirrors.163.com/ubuntu/ precise-security multiverse deb http://extras.ubuntu.com/ubuntu precise main deb-src http://extras.ubuntu.com/ubuntu precise main
2. Execute sudo apt-get update if it is still being given, the problem is that DNS is not configured
sudo gedit /etc/resolv.conf
Dynamic resolv.conf # ( 5 ) File for glibc the Resolver ( 3 ) Generated by resolvconf ( 8 ) # DO the NOT EDIT THIS FILE BY HAND - YOUR Overwritten the CHANGES WILL BE nameserver 127.0 . 1.1 # here is Ali cloud DNS server nameserver 223.5 . 5.5 nameserver 223.6 . 6.6
3. then sudo apt-get update on it