User and Group Management

1 how users exist with the system

/etc/passwd # Use information files

User name: User password: User uid : User gid: User description: User home directory: User-used Shell

/etc/shadow # user authentication information

User name: Password: Password Last modified date: Minimum validity: Password maximum validity: password warning period: Password inactive period: Password expiration Date:

/etc/group # User group Information

User group name: User Group password: User group ID: Additional user member

Initial group:

Additional groups: User-attached groups

/home/username # User home directory

/etc/skel/.* # Basic information configuration for users

Text Create new user is copy This file to user home directory

2. User Action Commands

ID View user Information

ID - u # # user uid

- G # # user gid

-A # # users All information

- G # # # users are all IDs

-un # # user name

-GN # # user Initial group name

-GN # # # users All group names

Su-username # # # Toggles the environment used by user users

Echo $PATH # # # View the user environment for the current user

Echo $USER # # # Displays information about the current user

3. Useradd # # # New user

- u # # # Specify uid for user

- G # # # Specify user initial group, this group must exist

- G # # # Specifies additional groups, and groups also exist

- C # # User Description

- D # # # Specify user plus directory

- S # # # Specify the shellThe user uses,shell type See /

Etc/shells Shell Type

4./etc/login.defs Default configuration when creating a user

Userdel - R # # # Delete users

Groupadd - G # # # New Group,-g indicates the ID of the specified group

Groupdel # # # Delete Group

passwd # # # change user password

5. view the commands used by the user to establish or manage the process

Watch-n 1 ' tail-3/etc/passwd;echo @@@@@@@@@@@@@@@@@@@@@@@@@@;tail-3/etc/group '

6. Usermod-u# # change user uid

- G # # change user initial group

- G # # change user-attached groups

-G "" # # Cancel all user groups

-ag # # Add user additional groups

- D # # change user home directory information

-MD # # change user home directory information and home directory name

- S # # change user's shell/sbin/nologin System user, not login

# # change user's description

- L # # freeze users

- u # # unlock users

Passwd-l Freezing user strength stronger

7. Devolution of user authority (sudo command Authority)

Configuration file for permission devolution action

/etc/sudoers

This file is edited with the visudo command ( directly with the command )

File contents

authorized target user host name =(new user identity granted to authorized users) authorizing users to execute commands

Test localhost=(root) Nopasswd:/usr/sbin/useradd

call with sudo

8. Password Age Change

User name: Password: Password Last modified date: Minimum validity: Password maximum validity: password warning period: Password inactive period: Password expiration Date:

chage - D 0 # # How long The secret is used, how to set it to 0 indicates that the user must change the password before logging on to the system

- M # # minimum validity

- M # # Maximum validity

- W # # warning period

- I. # # non-active period

- e # # expiry time format yyyy-mm-dd

User and Group Management