https://blog.gongquiz.com/2021/04/09/linux%ec%9d%98-%ed%8d%bc%eb%af%b8%ec%85%98permission%ec%97%90-%eb%8c%80%ed%95%9c-%ec%84%a4%eb%aa%85-%ec%a4%91-%ec%98%b3%ec%a7%80-%ec%95%8a%ec%9d%80-%ea%b2%83%ec%9d%80-%eb%84%a4%ed%8a%b8%ec%9b%8c/