Adding users to a group in Linux command line interface (CLI) is a simple task that can be accomplished with a few commands. This process is important for managing users and their permissions within a Linux system, as it allows for better control over who has access to certain resources and functionality.

Before diving into the process of adding a user to a group, it’s important to understand the basics of user and group management in Linux. In Linux, users are assigned a unique user ID (UID) and belong to one or more groups, which are identified by a group ID (GID). Groups are used to assign permissions to specific users or groups of users, allowing them to access certain resources or perform certain actions on the system.

Now that we have a basic understanding of how users and groups work in Linux, let’s dive into the process of adding a user to a group.

Adding a user to a group in Linux CLI can be done with the “usermod” command. The basic syntax of the command is as follows:

usermod -a -G [group name] [username]

The “-a” flag is used to append the user to the specified group, rather than replacing any existing groups. The “-G” flag specifies the group to which the user should be added. The [group name] and [username] should be replaced with the appropriate values for your system.

For example, if you wanted to add the user “john” to the group “users”, the command would be:

usermod -a -G users john

This command will add the user “john” to the group “users”, allowing him to access resources and perform actions that are assigned to that group.

It’s also possible to add a user to multiple groups at once by specifying multiple group names in the command. For example, if you wanted to add the user “john” to both the “users” and “admin” groups, the command would be:

usermod -a -G users,admin john

This command will add the user “john” to both the “users” and “admin” groups, giving him access to resources and functionality assigned to both groups.

Another important command for managing groups and users is the “groups” command. This command can be used to view the groups to which a specific user belongs. For example, if you wanted to see the groups to which the user “john” belongs, you would use the command:

groups john

This command would output a list of groups that the user “john” belongs to, such as “users” and “admin”.

It’s also possible to use the “id” command to view a user’s UID and GID. For example, if you wanted to see the UID and GID of the user “john”, you would use the command:

id john

This command would output information about the user “john”, including his UID and GID.

Another important command for managing users and groups is the “chown” command. This command can be used to change the ownership of a file or directory to a specific user or group. For example, if you wanted to change the ownership of a file called “test.txt” to the user “john” and the group “users”, the command would be:

chown john:users test.txt

This command would change the ownership of the file “test.txt” to the user “john” and the group “users”.

In addition to these commands, there are also several other tools and commands available for managing users and groups in Linux CLI. For example, the “useradd” command can be used to create new users, while the “groupadd” command can be used to create new groups. The “userdel” command can be used to delete users, and the “groupdel” command can be used to delete groups.

It’s also important to note that some Linux distributions, such as Ubuntu and Debian, have their own specific tools for managing users and groups. For example, Ubuntu uses the “adduser” and “deluser” commands for adding and deleting users, and Debian uses the “addgroup” and “delgroup” commands for adding and deleting groups.

In addition to these basic commands, there are also more advanced tools and scripts available for managing users and groups in Linux CLI. For example, the “ldapadd” command can be used to add users and groups to an LDAP directory, and the “pam-auth-update” command can be used to manage PAM authentication settings.

Overall, adding users to a group in Linux CLI is a simple task that can be accomplished with a few basic commands. Understanding how users and groups work in Linux and knowing the right commands to use can help you effectively manage and control access to resources and functionality on your system.