nano /etc/apt/sources.list.d/ubuntu.sources /etc/apt/sources.list

위 경로를 nano또는 vim같은 에디터로 연다음

kr.archive.ubuntu.com를 다른 서버로 변경하면된다

Mirrors : Ubuntu
Ubuntu also includes a wide variety of software through its network of software repositories. Once your system is installed you can simply call up a list of all the existing tools out there and choose any of them for immediate installation over the internet.
Launchpad