Adding Supplementary Groups to User Accounts in Linux

The useradd command in Linux is used to create a new user account. One of its options, -G or --groups, allows adding supplementary groups to a user account. This option is particularly useful when you want to grant additional group permissions to a user beyond their primary group.

Here are several examples illustrating the usage of useradd with the -G option:

Example 1: Adding a user ‘john’ and assigning supplementary groups ‘admin’ and ‘sudo’.

    $ sudo useradd -G admin,sudo john
    

This command creates a new user ‘john’ and adds him to the ‘admin’ and ‘sudo’ groups.

Example 2: Creating a user ‘alice’ and adding her to the ‘staff’ group.

    $ sudo useradd -G staff alice
    

Here, the user ‘alice’ is created with membership in the ‘staff’ group.

Example 3: Adding a user ‘sam’ to multiple groups ‘developers’ and ‘docker’.

    $ sudo useradd -G developers,docker sam
    

This command sets up the user ‘sam’ with both ‘developers’ and ‘docker’ group memberships.

Example 4: Creating a user ‘jane’ and adding her to ‘ftp’ group for file transfer permissions.

    $ sudo useradd -G ftp jane
    

Here, ‘jane’ is added to the ‘ftp’ group, typically used for FTP file transfers.

Example 5: Adding a user ‘bob’ to ‘audio’ group for sound device access.

    $ sudo useradd -G audio bob
    

This command grants ‘bob’ access to audio devices by adding him to the ‘audio’ group.

Example 6: Creating a user ‘tom’ and assigning him to ‘video’ group.

    $ sudo useradd -G video tom
    

Here, ‘tom’ is included in the ‘video’ group, useful for video device permissions.

Example 7: Adding a user ‘max’ to ‘games’ group for gaming-related access.

    $ sudo useradd -G games max
    

This command allows ‘max’ to access gaming-related resources through the ‘games’ group.

Example 8: Creating a user ‘sarah’ and assigning her to ‘docker’ and ‘wheel’ groups.

    $ sudo useradd -G docker,wheel sarah
    

Here, ‘sarah’ gains membership in both ‘docker’ and ‘wheel’ groups, enabling Docker and administrative privileges.

Example 9: Adding a user ‘tim’ to ‘mail’ group for email server access.

    $ sudo useradd -G mail tim
    

This command configures ‘tim’ with access to mail services through the ‘mail’ group.

Example 10: Creating a user ‘anna’ and assigning her to ‘finance’ group for financial data access.

    $ sudo useradd -G finance anna
    

Here, ‘anna’ is given access to financial data by joining the ‘finance’ group.

Verification Steps: To verify whether the user has been successfully added to the specified groups, you can use the id command followed by the username:

    $ id john
    uid=1001(john) gid=1001(john) groups=1001(john),27(sudo),5(admin)
    

In this output, the supplementary groups ‘sudo’ and ‘admin’ are listed under the groups section for user ‘john’, confirming the addition.