Linux Learning Notes (3) - Users and user groups

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user level

2 grade root, non-root

root highest authority, only a root user, the user name is root

Non-root restricted rights, can only access the root file specified

home directory

Log Users have their own file directory, usually / home / xxx, xxx note is the user name, the directory xxx is the user's home directory.

Outside the home directory is a public directory, usually read-only directory.

user group

A user can belong to multiple user groups, but have at least one user group. User group is actually similar to the concept of roles to describe what files users can access.

/ Etc / passwd to store user information

/ etc / passwd to store information about users, look as shown below:

Remove the line Analysis:

root	x	0	0	root	/root	/bin/bash
username	password	UID	GUIDE	Full name	home directory	shell

Note that the password is x, do not let you see the mean; UID User ID is a user ID, GID Group ID is a user group number; UID = 0 is a root user, GID = 0 represents the root user group.

/ Etc / group store user group

Use cat View user group information as follows:

This is relatively simple, we Analysis

root	x	0
User group name	password	GUIDE	User name in the user group

Note that within the user group user name, user name contains other information belonging to the group.

User and user group management

command	Features	Examples	Explanation
useradd	Add user	useradd tom	Need root privileges
passwd	Modify their own password	passwd xxx	After logging modification
passwd	Others modify the password	passwd tom	Need root privileges
userdel	delete users	userdel -r tom	And delete user home directory
groupadd	Add User Group	groupadd admin
groupdel	Deleting User Groups	groupadd admin
his	Switch User	are the
whoami	View the current user	whoami