What are Linux User Accounts?

In Linux, user accounts are used to manage access to system resources and provide a way to differentiate between various users. Each user account has its own set of permissions and configurations, allowing for secure and organized system management. User accounts can be categorized into system accounts and regular user accounts. System accounts are used by system services and applications, while regular user accounts are used by individuals.

What are User Groups?

User groups are collections of user accounts that are used to manage permissions and access to resources collectively. Instead of assigning permissions to individual users, you can assign them to a group. This way, any user who is a member of the group automatically inherits the permissions assigned to that group. This is particularly useful for managing file access and administrative privileges.

Each user can be a member of one or more groups, and each group can have multiple users. Groups simplify the management of user permissions and make it easier to apply changes across multiple users at once.

Creating a New User Account

To create a new user account, you use the useradd command. This command allows you to add a new user with default settings or specify additional options. Here’s how you can create a new user account:

sudo useradd -m username
sudo passwd username

In these examples:

• sudo useradd -m username creates a new user named username and creates a home directory for the user.
• sudo passwd username sets or changes the password for the user username.

Setting or Changing a User Password

To set or change a user's password, you use the passwd command. This command allows you to set a new password for an existing user account. Here’s how you can change the password:

sudo passwd username

In this command:

• sudo passwd username prompts you to enter a new password for the user username. You will need to enter the password twice to confirm.

Switching to Another User Account

To switch to another user account, you can use the su or sudo command. The su command is used to switch users, while sudo allows you to execute commands as another user.

su - username
sudo -u username command

In these examples:

• su - username switches the current session to the user username. You will be prompted for the user's password.
• sudo -u username command executes a specific command as the user username. This requires the current user to have the appropriate sudo permissions.

Deleting a User Account

To delete a user account, you use the userdel command. This command allows you to remove a user from the system. You can also choose to remove the user's home directory and mail spool.

sudo userdel username
sudo userdel -r username

In these examples:

• sudo userdel username deletes the user account username but leaves the user's home directory and files intact.
• sudo userdel -r username deletes the user account and also removes the user’s home directory and mail spool.

Creating a New User Group

To create a new user group, you use the groupadd command. This command creates a new group in the system:

sudo groupadd groupname

In this command:

• sudo groupadd groupname creates a new group named groupname.

Deleting a User Group

To delete a user group, you use the groupdel command. This command removes the specified group from the system:

sudo groupdel groupname

In this command:

• sudo groupdel groupname deletes the group named groupname. Note that you cannot delete a group that still has users in it; you must first remove the users or reassign them to another group.

Adding a User to a User Group

To add a user to a user group, you use the usermod command with the -aG option. This command adds the specified user to the specified group:

sudo usermod -aG groupname username

In this command:

• sudo usermod -aG groupname username adds the user username to the group groupname. The -a option appends the user to the group without removing them from other groups, and -G specifies the group.

Conclusion

Managing user accounts and user groups in Linux is essential for maintaining a secure and organized system. By understanding how to create, modify, and delete user accounts and groups, as well as how to manage group memberships, you can effectively control access to system resources and ensure proper security and organization.