What is a user account? Explain types of users . 

A user account is a systematic approach to track and monitor the usage of system resources. Each user account contains two unique identifiers; username and UID.

When a user account is created, its username is mapped to a unique UID.

Username is flexible. It can be changed as per requirement. Regardless it is selected first time or changed later; it must be unique in system. Two users can’t use the same username.

UID is fixed. It cannot be changed. Once assigned, it always remains the same for that user account.

Username is used to access the user account. Username is also known as login name. UID is used to authenticate, track and monitor the activity of user account. Username is used by the user while the UID is used by the system.

Types of user

There are three types of user in linux: - root, regular and service.

The root user account

This is the main user account in Linux system. It is automatically created during the installation. It has the highest privilege in system. It can do any administrative work and can access any service. This account is intended for system administration and should be used only for this purpose. It should not be used for routine activities. It can’t be deleted. But if require, it can be disabled.

The regular user account

This is the normal user account. During the installation, one regular user account is created automatically. After the installation, we can create as many regular user accounts as we need. This account has moderate privilege. This account is intended for routine works. It can perform only the tasks for which it is allowed and can access only those files and services for which it is authorized. As per requirement, it can be disabled or deleted.

The service account

Service accounts are created by installation packages when they are installed. These accounts are used by services to run processes and execute functions. These accounts are neither intended nor should be used for routine work.