How to Login as a Different User in Linux

Sometimes when I am working on a project and come across a new powerful Linux command, I need to test it. With a live dedicated server, that can be a recipe for disaster. Rather than taking such a risk with your websites and possibly the websites of customers (if you also host sites), I recommend creating test accounts.

A test user will have a unique set of configuration settings, its own home folder, and its own username and password. The second dilemma I encountered, however, was that once the account was created, I did not want to always have to log out of SSH and then login as the other user. In fact, for security reasons, I did not want the test user to have SSH access all.

Normally, the “su” command is used to become root, but you can also use it to login as any other user, directly from your SSH command prompt. To execute the command, type:

su -- username

It will then ask you for the specified user’s password. Enter it, and you are ready to test.

Image Source: Oxygen icons

Sudo vs. SU

The “su” command is what a Linux user with proper permissions uses to ascend to the root administrator account. A secure SSH server will not allow direct root login, so the user must gain root after initial login. The “sudo” command is an alternative to using a separate root user with its own password. Instead, the user prepends “sudo” before a command that needs root privileges. Certain distributions, such as Ubuntu use “sudo” by default, while others, such as CentOS, prefer “su”.

There are benefits and drawbacks to each. With “su”, root is a true separate user, and some administrators find it more useful to be able to log in as root and run several commands. With “sudo” only commands with those words in front of it will be administrative preventing the user from accidentally running a dangerous command as root.

There are security benefits to each, and the argument over which is better can get heated. Suffice it is to say that it ultimately depends on the preference of the system administrator. Does he/she want to deal with one password or two? Technically, an administrator can decide to use both on the same server and use the one that is most beneficial at the time. It can also be useful if you have multiple users who need various permissions.

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What is root and su?

Question: What is root and su?

Answer: On Linux and other Unix-like systems, root is the default username of the system administrator or super user (su). Typically, the root user is the only one that has complete read and write access on every file located on a server. Shared hosting accounts never allow root access, but if you are using a self-managed dedicated hosting service, you will probably need root access.

It is very unwise to login to your server directly as root. The more secure method is to login as a regular user with default permissions and then gain root access through the user. On Linux systems, you typically gain root access by typing “su” and then entering the password when prompted; however, some servers use sudo.

With sudo, you do not login directly as root. Instead, anytime you need to execute a root command, you put “sudo” in front of it. So, to remove a file, you would type “sudo rm filename”. It would then prompt you for the password. There has always been an ongoing to debate about which is more secure. With either method you need to be careful. Root has full access to your server. Use it wisely.

.SU celebrates 19 years

The .su ccTLD was delegated to the Soviet Union in 1990– just one year before its collapse. Though Russia eventually switched to the .ru suffix three years later, .su is still alive and kickin’. It celebrated its 19th birthday this week.

Today, there are more than 80,000 .su registrations. The extension grew 600% last year, though this growth has slowed down substantially as of late. It is also one of the first IDN extensions, allowing Russians to register domains in their native alphabet. Symbols from another 249 national languages are also supported.

The Soviet Union no longer exists on the map, but still has a place in the Internet age. Alexei Platonov, Director of Russian Institute for Public Networks (RIPN), summed up the extension’s importance quite well:

The .SU ccTLD was not delegated to the Soviet Union (although technically it was so). At that time, when the Soviet Union began to collapse, delegation meant the birth of new Internet community. So in fact, domain SU was like a guide and even a symbol of democratic development,

Source | Domain News