WHAT IS A GROUP? How to Managing and Creating Linux Group?

A group is a collection of users that need to share access to files and other system resources.

Groups can be used to grant access to files to a set of users instead of just a single user.

Like users, groups have group names to make them easier to work with. Internally, the system

distinguishes groups by the unique identification number assigned to them, the group ID or GID.

The mapping of group names to GIDs is defined in databases of group account information. By

default, systems use the /etc/group file to store information about local groups.Each line in the /etc/group file contains information about one group. Each group entry is

divided into four colon-separated fields. Here is an example of a line from /etc/group:

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group01:x:10000:user01,user02,user03

●          Group name for this group (group01).

●          Obsolete group password field. This field should always be x.

●          The GID number for this group (10000).

●          A list of users who are members of this group as a supplementary group (user01, user02,user03). Primary (or default) and supplementary groups are discussed later in this section.

Creating Groups from the Command Line

The groupadd command creates groups. Without options the groupadd command uses the next available GID from the range specified in the /etc/login.defs file while creating the

groups.

    [user01@host ~]$ sudo groupadd  10000 group01

Deleting Groups from the Command Line

• The groupdel command removes groups.

    [user01@host ~]$ sudo groupdel group0022

 

Modifying Existing Groups from the Command Line

• The groupmod command changes the properties of an existing group. The -n option specifies a

new name for the group.

 [user01@host ~]$ sudo groupmod -n group0022 group02

 

•             The -g option specifies a new GID.

  [user01@host ~]$ sudo groupmod -g 20000 group0022

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Written By Jitendar Kumar