Methods of creating users, switching users, and granting root privileges in Linux

References:

1. Linux user management (1) - create users (adduser and useradd) and delete users (userdel)
https://blog.csdn.net/beitiandijun/article/details/41678251

2. Usage and example of switching user identities su and sudo in Linux systemhttp
://blog.51cto.com/zebralinux/1369301

3. Under Linux, how to temporarily obtain root privileges for ordinary users to meet work needs.
http://blog.51cto.com/634871/1325907

4. Add users under linux and give root permissions
https://blog.csdn.net/stormbjm/article/details/9086163