ubuntu20.04 设置使用root用户登录系统

配置教程链接：

https://blog.csdn.net/COCO56/article/details/107628019?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522161226434516780261966510%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=161226434516780261966510&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_allfirst_rank_v2~rank_v29-2-107628019.pc_search_result_no_baidu_js&utm_term=ubuntu20.4使用root用户&spm=1018.2226.3001.4187