Tech Tutorial: Manage Users and Groups on RHEL #
Managing users and groups is a fundamental task for system administrators. In Red Hat Enterprise Linux (RHEL), this involves creating, deleting, and modifying local groups and their memberships. This tutorial is designed to help you prepare for the Red Hat Certified System Administrator (RHCSA) exam by providing detailed instructions and examples for managing users and groups on a RHEL system.
Introduction #
In RHEL, user and group management is typically handled through a set of command-line utilities. These tools allow you to add, remove, and alter user accounts and groups, as well as modify group memberships. Understanding these commands and their options is crucial for effective system administration.
Prerequisites #
- Access to a terminal on a RHEL system.
- Sudo or root privileges.
Step-by-Step Guide #
In this section, we will walk through the process of creating, deleting, and modifying local groups and managing group memberships.
1. Creating a Group #
To create a new group, use the groupadd command. The basic syntax is:
sudo groupadd [options] groupname
Example:
sudo groupadd developers
This command creates a new group named developers.
2. Deleting a Group #
To delete an existing group, use the groupdel command:
sudo groupdel groupname
Example:
sudo groupdel developers
This command deletes the group named developers. Be careful when deleting groups, as this cannot be undone.
3. Modifying a Group #
To modify an existing group’s attributes (such as its name), use the groupmod command:
sudo groupmod -n new_group_name old_group_name
Example:
sudo groupmod -n dev_team developers
This command renames the group developers to dev_team.
4. Creating a User and Adding to a Group #
To add a user and simultaneously assign them to a group, use the useradd command with the -G option:
sudo useradd -G groupname username
Example:
sudo useradd -G dev_team johndoe
This command creates a new user johndoe and adds them to the dev_team group.
5. Modifying User Group Membership #
To add or change a user’s group membership, use the usermod command:
sudo usermod -aG groupname username
Example:
sudo usermod -aG project1 johndoe
This adds johndoe to the project1 group without removing him from other groups.
6. Viewing Group Membership #
To view the members of a group, use the getent command:
getent group groupname
Example:
getent group dev_team
This displays the group ID and the members of dev_team.
Detailed Code Examples #
Here are some real-world scenarios using the commands discussed:
Scenario 1: Creating a Group for Developers
sudo groupadd developers
echo "Group 'developers' created."
Scenario 2: Deleting a Temporary Group
sudo groupdel temp_group
echo "Temporary group 'temp_group' deleted."
Scenario 3: Changing Group Name from ’test_group’ to ’test_team’
sudo groupmod -n test_team test_group
echo "Group name changed from 'test_group' to 'test_team'."
Conclusion #
In this tutorial, you learned how to manage users and groups in RHEL. You now know how to create, delete, and modify groups, as well as manage user memberships in groups. These skills are essential for system administration and are important for the RHCSA exam. Practice these commands to become proficient in user and group management on RHEL systems.