Linux Basics-Users and Groups

Basic information for users:/etc/passwd

User Shadow Password:/etc/shadow

Basic information for groups:/etc/group

Shadow password for group:/etc/gshadow

/etc/passwd file explanation [[email protected] ~]# cat/etc/passwdroot:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/ Nologindaemon:x:2:2:daemon:/sbin:/sbin/nologinadm:x:3:4:adm:/var/adm:/sbin/nologin the 7 columns above represent: 1, login 2, password placeholder 3, UID 4, GID 5, user information 6, user home directory 7, the user login shell

/etc/shadow file explanation [[email protected] ~]# cat/etc/shadowroot:$6$1hlftktqnwrfmdae$ pygewrfopin7pjoa3d3aymj37udveonqfnquzgufgq.8vfraelkchmc2w6seg5efc51hrlvli7s/dcjug6upu0:17105:0:99999:7:::bin:* : 15980:0:99999:7:::d aemon:*:15980:0:99999:7::: The columns above represent: 1, login 2, encrypt password, so the field is displayed as!! or * indicates that this user is locked 3, from 1970 to the password last modified the number of days elapsed 4, password minimum age 0 means no Limit 5, password maximum age 6, password expiring reminder

User Category:

Admin: UID is 0

Normal User: UID is 1-65535

System User: UID is 1-499

General User: Uid bit 500-65535

Group Category :

Private group: Create user Yes, if no owner is specified, a group with the same name as the user name is created automatically, and this group is the private group

Basic group: User's default genus Group

Additional groups: groups other than the base group

User Management related commands

Useradd, Usedel, Usermod, passwd, Chsh, ID, chage

Useradd: Adding users

Format: useradd [options] USERNAME

Useradd default configuration file:/etc/default/useradd

[[email protected] home] #useradd Yull

-U UID: Specifies user uid, requires greater than 500, and is not used

-G GID: Specifies the basic group GID, which requires the specified GID to exist beforehand

-C "STR": Specify user information, such as user name, phone, etc.

-d/path: Specify user home Directory

-s/bin/bash: Specifying the user-available shell

-R: Adding system users

ID: View user account attribute information

[Email protected] home]# Id-unroot

Parameters:

-G or--group displays the ID of the group to which the user belongs.

-G or--groups displays the ID of the additional group to which the user belongs.

-N or--name displays the name of the user, the owning group, or the additional group.

-R or--real displays the actual ID.

-U or--user displays the user ID.

-help display Help.

-version displaying version information

Userdel: Delete user, home directory is not deleted by default

[Email protected] home]# Userdel-r User01

-R USERNAME: Delete user and delete home directory

Usermod: Modify user account attributes, usage and useradd almost consistent

[Email protected] home]# usermod-u 1002 User01

-a-g GID: If the-a option is not applied, the user's previous additional groups will be overwritten

-d-m/path: Specify a new home directory and move the old home directory content to the new home directory. Common use of a piece

-L USERNAME: Modify user logon name

-E yyyy-mm-dd: Modify user Expiration Time

-L USERNAME: Lock user account

-U USERNAME: Unlock user account

Chsh: Modify with User Default shell

[Email protected] home]# Chsh user02changing shell for User02. New Shell [/bin/bash]:/bin/tcshshell changed.

passwd: User Password management

[Email protected] home]# echo "123456" | passwd--stdin user02changing password for user User02.passwd:all authentication tokens updated successfully.

--stdin: Avoid interactive input create password

-L USERNAME: Lock user

-U USERNAME: Unlocking password

-D USERNAME: Delete user password, delete password cannot login, but can Su

Group Management related commands

Groupadd, Froupdel, Groupmod, gpasswd

Groupadd: Adding groups

[Email protected] home]# Groupadd MyGroup

-R: Add system Group, ID less than bit 1-499, single no Home directory

Groupmod: Modifying Group properties

[Email protected] home]# groupmod-n mygroup01 mygroup

-G: Modify GID

-N: Modify Group name

This article from "Liang Childe" blog, please be sure to keep this source http://iyull.blog.51cto.com/4664834/1882854

Linux Basics-Users and Groups