Linux User and User Group Permissions

Each user has a unique ID number, and each group has a unique ID number.
The root user's number is 0, with the highest priority
The system user is 1-499, followed by priority
The average user is more than 500, and the maximum is more than 60 thousand,
By default, a user group with the same name and a folder with the same name under home are created. By default, this user belongs to this group, which is the main group of the user, one user can add 31 affiliated groups
User information is stored in/etc/passwd
The user password is stored in/etc/shadow.
The user group information is stored in/etc/group.

Id: this command is used to display the current user information.

[Www.bkjia.com @ localhost ~] $ Id
Uid = 500 (bkjia) gid = 500 (bkjia) groups = 500 (bkjia) context = unconfined_u: unconfined_r: unconfined_t: s0-s0: c0.c1023

Passwd is used to change the current user password.
Passwd user name to change the specified user password

Whoami view current user name
Who to view the current Login User
W. view the details of the currently logged-on user

[Root @ localhost etc] # whoami

Root

[Root @ localhost etc] # who

Bkjia tty1 2013-05-26 20:14 (: 0)

Bkjia pts/02013-05-26 (: 0.0)

Bkjia pts/12013-05-26 (192.168.200.151)

[Root @ localhost etc] # w

20:53:51 up 41 min, 3 users, load average: 0.02, 0.01, 0.02

User tty from login @ IDLE JCPU PCPU WHAT

Bkjia tty1: 0 41: 09 14.51 s 0.17 s pam: TPD-passwo

Bkjia pts/0: 0. 0 0.41 s 0.76 s gnome-terminal

Bkjia pts/119425200.151 0.00 s 0.16 s 0.23 s login -- bkjia

Useradd Add a user name

-D specifies the user directory

-S logon shell

-G: Specifies the master group.

-G: Specify the affiliated group

 

Usermod new username change Username

Usermod-L ljj prevents user ljj from logging on

-U allows users to log on

-G: Modify the user master Group

-G: Modify user group

-D. Modify the user's home directory

-U: Modify the user ID

 

 

Userdel user name delete user but keep user directory

Userdel-r user name delete user and delete user directory

 

Add a group by groupadd group name

Groupmod-n new group name modify group name

Groupmod-g new id ID modify group ID

Groupdel group name Delete Group