1.
mkdir ~/solution
cd ~/solution/
2.
vi로 ~/solution/sources.list 연 다음에 아래 내용 넣고 저장
deb http://archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
deb http://archive.canonical.com/ubuntu focal partner
deb-src http://archive.canonical.com/ubuntu focal partner
3.
sudo mv /etc/apt/sources.list.d/* ~/solution
sudo apt update
+) update는 잘 되는데, install 하고자 하는 것들을 apt-get 혹은 apt로 설치하면 잘 안된다.
sudo apt-get install -y aptitude로 aptitude를 깔고 apt-get 대신 aptitude로 사용하면 apt-get을 대체하여 설치할 수 있다