User, Group, and Rights management

User, Group, and Rights management

Multi-tasks, Multi-users

Per User:

User ID, password;

Authentication

Authorization

Audition

Group: User groups, user containers

User Category:

Administrator

Normal User

System users

Logged in user

User id: UserID, UID

16bits binary Number: 0-65535

Admin: 0

Normal Users: 1-65635

System User: 1-499 (CentOS6), 1-999 (CentOS7)

Login User: 500-60000 (CentOS6), 1000-60000 (CentOS7)

Name resolution: Name translation

Username <--> UID

Based on the name resolution library:/ETC/PASSWD

Group:

Group Category 1:

Administrators group

General user groups

System Group

Login Group

Group ID: GroupID, GID

Administrators group: 0

Normal User group: 1-65635

System User group: 1-499 (CentOS6), 1-999 (CentOS7)

Login User group: 500-60000 (CentOS6), 1000-60000 (CentOS7)

Name resolution: GroupName <--> GID

Analytic Library:/etc/group

Group Category 2:

Basic Group of users

Additional Groups for users

Group Category 3:

Private group: The group name is the same as the user name and contains only one user;

Public group: Multiple users are included in the group;

Certification information:

Whether the information provided by the login is consistent with the prior storage of the data;

Password

/etc/shadow

/etc/gshadow

Password Usage Policy:

1, the use of random password;

2, the shortest length is not less than 8 bits;

3, should use uppercase letters, lowercase letters, numbers and punctuation characters of at least three classes;

4, regular replacement;

Encryption algorithm:

Symmetric encryption: Encryption and decryption using the same password;

Asymmetric encryption: A pair of keys used for encryption and decryption;

Key pair:

Key: Public key

Private key:

One-way encryption: can only encrypt, not decrypt; extract data signatures;

Fixed-length output

Avalanche effect

Algorithm:

Md5:message Digest, 128bits

Sha:secure hash Algorithm, 160bits

sha224

sha256

sha384

sha512

Add salt at the time of calculation, random number added;

/ETC/PASSWD: User's information base

Name:password:UID:GID:GECOS:directory:shell

Name: User Name

Password: Can be encrypted password, but also placeholder X;

Uid:

GID: The ID number of the primary group to which the user belongs;

GECOS: Comment Information

Directory: The user's home directory;

Shell: The default shell of the user, the default shell program when logging in;

/etc/shadow: User Password

User name: Encrypted password: The last time the password was modified: Minimum Age: Maximum Age: Warning Period: Expiration period: Reserved field

/etc/group: Information Base for groups

Group_name:password:GID:user_list

User_list: The user member of the group; the user list of users with this group as an additional group;

Related commands: Useradd, Userdel, Usermod, passwd, Groupadd, Groupdel, Groupmod, gpasswd, Chage, Chsh, id, su

User, Group, and Rights management