Linux Operations Essentials UNIT5

Unit5

1. User understanding

* User is the identity of the system users

* Users stored in the system as a number of channeling characters + several system configuration files

User information involves the system configuration file:

1./etc/passwd # # #用户信息

User: Password:uid:gid: Description: Home directory: User-used Shell

2./etc/shadow # # #用户认证信息

User: Password: Last password modified this time: Minimum validity: Maximum validity: Warning Period: Inactive period: Account expiration date

3./etc/group # # #组信息

Group name: Group Password: Group ID: Additional Group member

4./etc/gshadow # # #组认证信息

5./home/username # # #用户家目录

6./etc/skel/.* # # #用户骨架文件

View tail-n /etc/*

2. User Management

> 1. User established Useradd user name

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Useradd Parameters User name

- u # #指定用户uid

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- G # #指定用户初始组信息, this group must already exist

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- G # #指定附加组, this group must exist

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- C # #用户说明

- D # #用户家目录

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- S # #用户所使用的shell,/etc/shells records the name of the user who can use the shell

>2. User Delete

Userdel - R User name -r means delete user information and user's system configuration

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3. Establishment of groups

Groupadd - G # #建立组

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Groupdel Group name # #删除组

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Monitoring commands for the above experiments:

Watch-n 1 ' tail-n 3/etc/passwd/etc/group;echo ====;ls-l/home;echo ===;ls-l/mnt '

4. User ID Information view

ID Parameters User

- u # #用户uid

- G # #用户初始组id

- G # #用户所有所在组id

- N # #显示名称而不是id数字

-A # #显示所有信息

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5. Changes to user information

Usermod Parameters User

- L # #更改用户名称

- u # #更改uid

- G # #更改gid

- G # #更改附加组

-ag # #添加附加组

- C # #更改说明

- D #更改家目录指定

-MD # #更改家目录指定及家目录名称

- S # #更改shell

- L #冻结帐号

- u # #解锁

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3. User decentralization

1. In the system, Superuser can delegate actions that ordinary users cannot perform to ordinary users.

Delegated Authority Profile:/etc/sudoers

2. Ways of delegating authority

*) Super User execution Visudo enter edit/etc/sudoers mode

*) Format:

Get rights users Host Name = (acquired user identity) Command

Test desktop0.example.com= (Root) /usr/sbin/useradd

Test user can execute/usr/sbin/useradd as Superuser in desktop0.example.com

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3. Implementation of the delegation of authority command

sudo Command # #如果第一次执行sudo需要输入当前用户密码

in /etc/sudoers if the settings are as follows:

Test desktop0.example.com= (Root) nopasswd:/usr/sbin/useradd

indicates that the user does not need their own password when invoking the sudo command

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4. Control of user authentication information

chage Parameters User

- D # #用户密码组后一次修改的时间, if set to 0, users must change their password after logging into the system

- M # #最短有效期

- M # #最长有效期

- W # #警告期

- I. # #用户非活跃天数

- e # #帐号到期日格式-E "Yyyy-mm-dd"

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Linux Operations Essentials UNIT5