Concept of SuperUser in Linux

You might have read my last article which explained the steps of installing Linux with the help of VirtualBox. Now, we are going to see some tricky stuff on Linux. Linux is mainly used in creating servers and building different OS like Android. But before we go that deep, our concepts about an Operating System must be clear. Don't worry as we are not going so hard with Operating Systems but the clearance of basics is must..!

You might have heard about rooting your Android device gives you much extra features on your device. Also, after installing Linux on your PC, one might have a question about how to install Linux on Android device. To learn all these, the knowledge about the concept of superuser is important. So, let's start.

You might have seen the phrase - "Install (as superuser)" written on top-left of the screen when installing Linux. That means that when you are installing an OS, the OS is first installed as superuser mode and then you create separate accounts as per your use. You might be aware about the word "administrator" when using windows OS. The admin account is the one, which has a complete control over the system and files in the system. Though Windows doesn't permit a total control to an admin account too as it is not an open-source project. But this is not the case with Linux.

In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of the account is not the determining factor; on Unix-like systems, for example, the user with a user identifier (UID) of zero is the superuser, regardless of the name of that account. That means, in Unix-like systems, we can rename a superuser account name (generally named root) to the name we want. Its because, the name of account is not of prime importance. The system identifies a user account by a unique identification number called UID. Hence, renaming the account will not change its ID.

The word root also has several additional, related meanings when used as part of other terms, and thus it can be a source of confusion to people new to Unix-like systems.

One of these is the root directory, which is the top level directory on a system. That is, it is the directory in which all other directories, including their subdirectories, and files reside. The root directory is designated by a forward slash ( / ). 

Another is /root (pronounced slash root), which is the root user's home directory. A home directory is the primary repository of a user's files, including that user's configuration files, and it is usually the directory in which a user finds itself when it logs into a system. /root is a subdirectory of the root directory, as indicated by the forward slash that begins its name, and should not to be confused with that directory. Home directories for users other than root are by default created in the /home directory, which is another standard subdirectory of the root directory.

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After trying to open the root user's home directory, you might be having a question that why aren't you able to open the directory even if you are logged in as the administrator. As I said before, admin and root are two different terms with same meaning. Hence, you should be able to open the /root subdirectory, but it is not happening. This is because, linux also cares about its security when providing you control over it. Messing with the files inside /root directory may be harmful for the system and leave a negative impact. That is why Linux has blocked you from accessing the /root directory. You will know about it more when we study shell scripting in Linux. There are two commands namely "su" (SuperUser) and "sudo" (Superuser Do). The su command is used by the root users having access to /root directory while the sudo command is used by the admin who hasn't granted root privileges.

Root privileges are the powers that the root account has on the system. The root account is the most privileged on the system and has absolute power over it (i.e., complete access to all files and commands). Among root's powers are the ability to modify the system 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 root account with root privileges assigned has the power to access /root directory. Here, the whole case is similar to admin account in Windows. Though you are the admin, you will be prompted to open any file with admin privileges. Or else, you have to right-click on the file and select "run as administrator" to grant the file administrator privileges. But when you activate a separate administrator account in windows (it is always hidden by default for the case of security), you will never be prompted or you never have to grant any file administrator permission. This is because, the system trust all the tasks performed by the administrator. There is always a difference between your account type "admin" and the administrator account itself.

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A rootkit is a set of software tools secretly installed by an intruder into a computer that allows such intruder to use that computer for its own, usually nefarious, purposes when desired. Well designed rootkits are able to obtain root access (i.e., access to the root account rather than just to a user account) and to hide most or all traces of their presence and activities. 

The use of the term root for the all-powerful administrative user may have arisen from the fact that root is the only account having write permissions (i.e., permission to modify files) in the root directory. The root directory, in turn, takes its name from the fact that the filesystems (i.e., the entire hierarchy of directories that is used to organize files) in Unix-like operating systems have been designed with a tree-like (although inverted) structure in which all directories branch off from a single directory that is analogous to the root of a tree.

These things aren't easily understandable. You might be still having doubts like difference between gaining root access and having an administrator (root) account. Also, you might be wondering about how to gain root privileges by activating the hidden root account. All such questions will be cleared in my next article where I will show you how to activate the root account to get root pemissions. And then we will try to open the /root directory with that account.

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