Detailed parameters of the command man page or help view. This is just a list, you can understand these commands.
1. User management of several commonly used commands
Commonly used commands: useradd passwd the usermod userdel the above mentioned id
Information related to the user's file
/etc/passwd
/etc/shadow
Associated with the user group information file
/etc/group
/etc/gshadow
2. The process management-related commands
bg fg kill killall pkill pgrep ps top pstree screen
3. Check the system disk of the order
df
