How to Manage Users on AlmaLinux Add, Remove, and Modify

1. Understanding User Management in AlmaLinux

User management in AlmaLinux involves controlling who can access the system, what they can do, and managing their resources. This includes adding new users, setting passwords, assigning permissions, and removing users when no longer needed. AlmaLinux uses the Linux kernel’s built-in user management commands like adduser, usermod, passwd, and deluser.

2. Adding a New User

AlmaLinux provides the useradd command for creating a new user. This command allows you to add a user while specifying their home directory, default shell, and other options.

Steps to Add a New User:

1. Open your terminal and switch to the root user or a user with sudo privileges.
2. Run the following command to add a user:

sudo useradd -m -s /bin/bash newusername

• m: Creates a home directory for the user.
• s: Specifies the shell (default: /bin/bash).

3. Set a password for the new user:

sudo passwd newusername

4. Verify the user has been created:

cat /etc/passwd | grep newusername

This displays details of the newly created user, including their username, home directory, and shell.

3. Modifying User Details

Sometimes, you need to update user information such as their shell, username, or group. AlmaLinux uses the usermod command for this.

Changing a User’s Shell

To change the shell of an existing user:

sudo usermod -s /usr/bin/zsh newusername

Verify the change:

cat /etc/passwd | grep newusername

Renaming a User

To rename a user:

sudo usermod -l newusername oldusername

Additionally, rename their home directory:

sudo mv /home/oldusername /home/newusername
sudo usermod -d /home/newusername newusername

Adding a User to a Group

Groups allow better management of permissions. To add a user to an existing group:

sudo usermod -aG groupname newusername

For example, to add the user newusername to the wheel group (which provides sudo access):

sudo usermod -aG wheel newusername

4. Removing a User

Removing a user from AlmaLinux involves deleting their account and optionally their home directory. Use the userdel command for this purpose.

Steps to Remove a User:

1. To delete a user without deleting their home directory:

sudo userdel newusername

2. To delete a user along with their home directory:

sudo userdel -r newusername

3. Verify the user has been removed:

cat /etc/passwd | grep newusername

5. Managing User Permissions

User permissions in Linux are managed using file permissions, which are categorized as read (r), write (w), and execute (x) for three entities: owner, group, and others.

Checking Permissions

Use the ls -l command to view file permissions:

ls -l filename

The output might look like:

-rw-r--r-- 1 owner group 1234 Nov 28 10:00 filename

• rw-: Owner can read and write.
• r--: Group members can only read.
• r--: Others can only read.

Changing Permissions

• Use chmod to modify file permissions:

sudo chmod 750 filename

• 750 sets permissions to:

  • Owner: read, write, execute.
  • Group: read and execute.
  • Others: no access.

• Use chown to change file ownership:

sudo chown newusername:groupname filename

6. Advanced User Management

Managing User Quotas

AlmaLinux supports user quotas to restrict disk space usage. To enable quotas:

• Install the quota package:

sudo dnf install quota

• Edit /etc/fstab to enable quotas on a filesystem. For example:

/dev/sda1 / ext4 defaults,usrquota,grpquota 0 1

• Remount the filesystem:

sudo mount -o remount /

• Initialize quota tracking:

sudo quotacheck -cug /

• Assign a quota to a user:

sudo setquota -u newusername 50000 55000 0 0 /

This sets a soft limit of 50MB and a hard limit of 55MB for the user.

7. Creating and Using Scripts for User Management

For repetitive tasks like adding multiple users, scripts can save time.

Example Script to Add Multiple Users

Create a script file:

sudo nano add_users.sh

Add the following code:

#!/bin/bash
while read username; do
    sudo useradd -m -s /bin/bash "$username"
    echo "User $username added successfully!"
done < user_list.txt

Save and exit, then make the script executable:

chmod +x add_users.sh

Run the script with a file containing a list of usernames (user_list.txt).

8. Best Practices for User Management

1. Use Groups: Assign users to groups for better permission management.
2. Enforce Password Policies: Use tools like pam_pwquality to enforce strong passwords.
3. Audit User Accounts: Periodically check for inactive or unnecessary accounts.
4. Backup Configurations: Before making major changes, back up important files like /etc/passwd and /etc/shadow.

Conclusion

Managing users on AlmaLinux is straightforward when you understand the commands and concepts involved. By following the steps and examples provided, you can effectively add, modify, and remove users, as well as manage permissions and quotas. AlmaLinux’s flexibility ensures that administrators have the tools they need to maintain a secure and organized system.

Do you have any specific user management challenges on AlmaLinux? Let us know in the comments below!