How to Change User in Linux Command Line

Linux systems have a robust user management system where different users can have different levels of permissions. Understanding how to switch users in Linux is essential for efficiently managing tasks, especially when certain commands or operations require elevated privileges or a different user environment.

In this article, we’ll cover how to change users in the Linux command line, explain the different types of users, and provide useful examples to make the concept easier to grasp.

To switch to another user in Linux, you need to know that user’s password. The basic command to switch users is:

su -

If you want to switch to the root user in Ubuntu, you can use:

sudo -i

We’ll dive into more details about these commands below.

Types of Users in Linux

Linux systems classify users into three broad categories:

1. System Users

System users are created automatically during the installation of Linux or when new services and applications are installed. These users run background processes or system-level tasks. Examples include users like `nobody`, `www-data`, or `mysql`.

2. Regular Users

These are the users created for human interaction. Each regular user has their own home directory and can log in to the system.

3. Super Users

Super users (e.g., root) have unrestricted access to the system. They can perform critical tasks, such as installing software, modifying system configurations, or managing other users.

When logged into a Linux system, you can switch to another user within the same terminal session using the `su` command. Here’s how it works:

johndoe@system:~$ su - janedoe
Password:
janedoe@system:~$

Switching to the Root User

The root user is the most powerful account in a Linux system. However, for security reasons, direct login as the root user is often disabled on many systems.

Using `sudo`

To perform root-level operations, you can use the `sudo` command. With `sudo`, you don’t need to know the root user’s password. Instead, your user must be part of the `sudoers` group, and you’ll use your own password to authenticate.

Run a Single Command as Root:

sudo

Example:

sudo apt update

Switch to Root User:

If you want to switch to the root user and remain logged in for multiple commands, use:

sudo -i

– You’ll be prompted to enter your own password, not the root’s password.
– Once logged in, all subsequent commands will be executed as the root user until you exit the session.

Listing All Users

To view all users on a Linux system, you can check the `/etc/passwd` file:

cat /etc/passwd

This will display a list of all system and regular users. For example:

root:x:0:0:root:/root:/bin/bash
johndoe:x:1000:1000:John Doe:/home/johndoe:/bin/bash
janedoe:x:1001:1001:Jane Doe:/home/janedoe:/bin/bash

– The first field is the username.
– System users typically have lower UID (User ID) numbers, while regular users have higher UIDs.

Best Practices When Switching Users

1. Avoid Using Root Unnecessarily: Use `sudo` to execute specific commands rather than logging in as root.
2. Secure Your System: Ensure that only trusted users are added to the `sudoers` group.
3. Use Descriptive Usernames: This helps in managing and identifying users easily.
4. Exit Sessions: After completing tasks as another user, type `exit` to return to the previous user or session.

Conclusion

Switching users in Linux is a fundamental skill for managing tasks effectively. Whether you’re performing a system-level task as a superuser or troubleshooting as another regular user, the `su` and `sudo` commands provide the flexibility to change users securely.

Remember: With great sudo power comes great responsibility! Always use elevated privileges cautiously to avoid unintended system changes.

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