Presentation Hidaya

7/29/2019 Presentation Hidaya

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USERS & GROUPS IN LINUX

SALMAN ARAIN

ID # 3749


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OUTLINES:

Users & Groups

How to Create User & Groups

How to add a particular user in a group

Some useful commands and options.


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USERS:

The control ofusers andgroups is a core

element of Fedora system administration.

Users can be either people or accounts

which exist for specific applications to

use.


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GROUPS:

Groups are logical expressions oforganization, tying users together for acommon purpose.

Users within a group can read, write, orexecute files owned by that group.

Each user is associated with a unique

numerical identification number called auserid(UID); likewise, each group isassociated with agroupid(GID).


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CONTD:

A user who creates a file is also the ownerand group owner of that file.

The file is assigned separate read, write, and

execute permissions for the owner, thegroup, and everyone else.

The file owner can be changed only by the

root user, and access permissions can bechanged by both the root user and fileowner.


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CONTD:

By default, all users home directory iscreated & maintained in /home directoryand root user home directory is at /root.

The first regular user account created onthe system always assigned a UID of 500 andso on, and the root user account is alwayshave a UID of 0.

Its this UID that the operating systemactually uses to control access to files anddirectories in the file system.


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Some Important Files


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USER MANAGEMENT:

Using useraddSyntax: useradd options username

Using passwd

Syntax: passwd options username

Using usermod

Syntax: usermod options username

Using userdel

Syntax : userdel options username


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Some Useful Options for Useradd :

-c Add a description about the user

-d Specify the home directory of user

-e Define expiry date of user account

-g Specify the primary group of useraccount.

-G Specify the supplementary groups

-M Ensure that users home directory isnot created

-n specify user id


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Some useful Options for usermod:

-c Modify description of user account

-d Modify home directory

-e Modify account expiry date

-g Modify the primary group

-G Modify the supplementary groups

-l Modify the login name of an existing user account

-u Modify a user-id of a user account

-L Lock an existing user account

-U Unlock a locked user account


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Userdel option:

By default, userdel will not remove the usershome directory from the file system.

To remove that from home directory, whenyou delete the user, you need to use the r

option in the command line.

For instance, userdel r username

userdel f username


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GROUP MANAGEMENT:

Using groupadd

Syntax: groupadd options groupname

Using groupmodSyntax: groupmod options file

(-n, -g)

Using groupdel

Syntax: groupdel groupname


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LINUX gpasswd command for

Group Management:

Linux systems provide the gpasswd command for adding andremoving members of groups and for specifying groupadministrators.

# gpasswd -a aqeel talha

# gpasswd d aqeel talha

The -A and -M options are used to specify the list of groupadministrators and additional group members.

# gpasswd -A salman muet

The list of users specified as the argument to either option iscomma-separated and must not contain any internal spaces.


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