https://itlearningcenter.tistory.com/entry/%E3%80%90Ubuntu-2004-LTS%E3%80%91%EC%B9%B4%EC%B9%B4%EC%98%A4%ED%86%A1-%EC%84%A4%EC%B9%98-1
https://velog.io/@duboo/Ubuntu-20.04-%EC%B9%B4%EC%B9%B4%EC%98%A4%ED%86%A1-%EC%84%A4%EC%B9%98%EB%B0%A9%EB%B2%95-%ED%95%9C%EA%B8%80%EA%B9%A8%EC%A7%90-%EB%AC%B8%EC%A0%9C