What is Root User in Linux?

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The root is the user name or account that is by default has access to all commands and files on a Linux or other Unix-like OS. It is also referred to as the root account, root user, and the superuser in Linux.

The root user is also known as the superuser or administrator, it is a special user account in Linux used for the system administration. It is the most privileged user on the Linux system Environment and it has access to all the commands and files. The root user can do many things that an ordinary user cannot, such as installing a new software, changing the ownership of the files, and managing other user accounts.

It is not recommended to use root for the ordinary tasks, such as browsing the web, writing texts, e.g. A simple mistake can cause problems with the entire environment, for example if we mistype a command. It is advisable to create a normal user account for such tasks and assogn required permissions. If root permissions are needed, then the su and sudo commands can be used.

Privileges & Permissions

Root privileges are the powers that the root account has on the environment. The root account is the most privileged on the system OS and has absolute power over it (i.e., complete access to all the files and commands). Among root's powers are the ability to modify the system environment in any way desired and to grant and revoke access permissions (i.e., the ability to read, modify and execute specific files and directories) for other users, including any of those that are by default reserved for root.

The permissions system in Unix-like operating systems such as Linux is set by default to prevent access by ordinary users to the critical parts of the system and to files and directories belonging to the other users. This is because it is very easy to damage a Unix-like system with having root access. However, an important principle of Unix-like operating systems is the provision of maximum flexibility to configure the system OS, and thus the root user is fully empowered.

Use with Caution

Linux systems assume that the system administrator knows exactly what he or she is doing and that only such individual(s) will be using the root account to access. Thus, there is virtually no safety net for the root user in the event of a careless error, such as damaging or deleting a critical system file (which could make the entire system inoperable). For this reason, we would strongly encourage you to make backups of any files/directories you are working with.
Adding to the danger of routinely using the system as root is the fact that all processes (i.e., instances of programs in execution) started by the root user have root privileges. Because even the most widely used and well-tested application programs contain numerous programming errors (due to the huge amount of code required and its great complexity), a skilled attacker can often find and exploit such an error to obtain control of a system when a program is run with root privileges rather than using an ordinary user account, with its very limited privileges.
A critical means for preventing users from directly damaging Unix-like systems or increasing the vulnerability of such systems to damage by others is the avoidance of using the root account except when absolutely necessary, even by knowledgeable and experienced system administrators. That is, rather than routinely logging into the system as root, administrators should log in with their admin account and then use the su command. This will provide you with root privileges only as needed and without requiring a new login.

When to use root

Tasks that require root privileges include moving files or directories into or out of system directories (i.e., directories that are critical to the functioning of the operating system), copying files into system directories, granting or revoking user privileges, some system repairs, and the installation of some application programs. By default, it is not necessary to be root to be able to read most configuration files and documentation files in system directories, although it is necessary to be root to modify them.
Root privileges are usually required for installing software in RPM (Red Hat Package Manager) package format because of the need to write to system directories. If an application program is being compiled (i.e., converted into runnable form) from source code (i.e., its original, human-readable form), however, it can usually be configured to install and run from a user's home directory. Root privileges are not needed by an ordinary user to compile and install software in its home directory. Compiling software as root should be avoided for security reasons.