How to Change User in Linux: A Comprehensive 2021 Guide

Linux is the leading open-source operating system powering modern infrastructures. According to the Linux Foundation, over 80% of companies leverage Linux in their technology stacks. With its multi-user capabilities, Linux drives majority of enterprise systems, web servers, cloud platforms and embedded devices across the globe.

Having robust user management is critical for security and access control in multi-user Linux environments. Let‘s analyze key aspects of users in Linux systems.

Linux Users and Use Cases

Linux manages user accounts to compartmentalize access to system resources. There are three types of Linux users:

1. System Users: Accounts utilized by background processes and services. Created during Linux installation.

2. Standard Users: Accounts for humans to login and access system resources. Can be created/deleted as per access needs.

3. Root user: The superuser account with unrestricted access to all system files, resources and administrative privileges.

Separating standard user and admin privileges is vital for security. According to 2020 statistics, over 50% of all data breaches originate from human errors of privileged insiders.

Hence properly configuring and isolating Linux users is important, especially in multi-user environments like:

• Enterprise servers accessible by many admins.
• Academic/organizational networks with thousands of individual users.
• Public cloud platforms allowing customer tenant logins.
• IoT devices and embedded systems deployed globally.

Now let‘s go through steps to switch between users in Linux for day-to-day tasks or during critical troubleshooting.

Change User in Linux Command Line

The Linux command line interface (CLI) provides simple administrator commands to change users within active shell sessions. These CLI utilities are universally available across all Linux distros and environments.

su command: Switch User in Linux Terminal

The su command allows switching to another user account during an interactive CLI or terminal session.

Its syntax is:

su [OPTIONS] [USERNAME]

To change from current user to a target user, run:

$ su newuser

When executed, su will prompt for the password of the destination account before changing the user.

Some key characteristics of su command:

• Requires target user‘s password for elevated account switching.
• Offers no timestamp or audit logs for security policy compliance.
• Launches shells with complete user permissions and environment variables.
• Changes user for just that CLI session, not entire operating system.

If no username is passed, su defaults to root account. So following commands are same:

$ su
$ su root 

Security Tip: Avoid staying logged in as root through su for longer durations. Use sudo wherever possible as it offers more granular control and enhanced security.

sudo Command: Run Commands as Another User

The sudo command allows running single commands or shells as other users, by default as root. To change users with sudo:

sudo -u user -i 

For example, to switch logged in user to john:

sudo -u john -i

Key sudo characteristics:

• Needs target user‘s password.
• Maintains logs of all commands via /var/log/sudo/
• Launches shell with user‘s environment variables.
• Can configure fine-grained privilege escalation policies.

You can also execute single commands avoiding full login:

sudo -u user command 

So sudo enables administrators to run commands or shells as any standard Linux user. This improves troubleshooting productivity in complex multi-user systems.

Switch Users in Linux Desktop Environments

Modern Linux distributions come with intuitive graphical desktops like GNOME, KDE for improved usability:

These desktop environments include inbuilt capabilities to easily switch between signed-in user accounts.

Change User in GNOME

The GNOME Project powers the most popular Linux desktop environment. Here are steps to change users in GNOME:

1. Click user menu (power button) on top right and select Switch User option.

2. Choose target user account from the list.

   

3. Login screen prompts for user password.

4. Enter credentials and click Sign In to switch accounts.

This avoids sign out of active GNOME sessions and logs in parallel user accounts.

Change User Account in KDE Plasma

KDE Plasma focuses on providing extreme customization and flexibility options for Linux users. To switch accounts in KDE:

1. Click Leave button on bottom left.

2. Select Switch User option.

   

3. Choose desired user account from the dialog.

4. Type in account password when prompted.

So KDE Desktop also enables fast user switching between multiple active Plasma sessions.

Switch User in Cinnamon Desktop

Developed by Linux Mint, Cinnamon focuses on a classic user experience. Follow below steps for account change:

1. Right click user applet showing current user details.

2. Pick Switch User entry.

   

3. Select the target user account.

4. Input password when prompted to login.

This will sign-in the chosen user without closing existing Cinnamon desktop sessions.

Comparative Analysis of Desktop Environments:

Desktop	Switch User Mechanism	Extra Info
GNOME	From user menu	Most intuitive controls
KDE Plasma	Via Leave button	More steps than GNOME
Cinnamon	User applet context menu	Straightforward for new users

So all major Linux desktops offer efficient utilities to handle user account switching.

Switch User with Linux Display Managers

Display managers provide graphical login screens and authenticate user access in Linux:

They include options to change signed-in users without fully logging out active desktop sessions.

For example – Switch User in LightDM:

1. Click user menu.

2. Choose Switch User Account.

3. Select user from dialog.

4. Type credentials when prompted.

   

Benefits of using Display Managers for User Switching:

• Support for parallel graphical sessions.
• Centralized access controls via PAM (Pluggable Authentication Modules).
• Authentication against NSS, LDAP, SSSD identity stores.
• Custom branding and theming capabilities.

So display managers provide enhanced controls for multi-seat user change requirements in Linux systems.

Advanced User Switching with PAM

The Linux-PAM library controls authentication conversations in Linux. PAM configuration files in /etc/pam.d/ specify how user logins occur.

The pam_exec module lets running external scripts during PAM auth events. We can utilize it to trigger automatic user switching rules:

/etc/pam.d/common-auth

auth requisite pam_exec.so /usr/local/bin/changeuser.sh

The changeuser.sh script will have custom logic for user account changes.

Benefits of the PAM Method:

• Granularly configure auth and session policies.
• Integrate with tools like SSSD, AD, LDAP.
• Domain-wise or location-based rules.
• Desktop environment or display manager agnostic.

So Linux-PAM offers advanced capabilities to customize user switching in specialized use cases.

Additional Methods to Change Users

There are some other ways to change users in Linux systems:

• Remote Login Protocols: Linux supports remote authentication protocols like SSH, Telnet, FTP. These facilitate admin login from other hosts for user switching.
• Ctrl + Alt + F[1-6]: Change between virtual consoles in CLI, allowing logins of different users.
• Useradd/Delete: Create or remove user accounts through useradd/userdel commands.
• Scripting: Scheduling cronjobs or writing custom scripts to automate user management policies.

So there are many approaches to streamline Linux user transitions depending on specific environment needs.

Conclusion

We thoroughly explored various utilities and techniques to change users in Linux machines:

• su and sudo CLIs for fast administrative account switching.
• Graphical controls given by GNOME, KDE, Cinnamon desktop environments.
• Switch user features present in display managers like LightDM, SDDM etc.
• Advanced PAM customization for granular user transition policies.
• Additional protocols like SSH, virtual consoles to remotely access accounts.

Smooth user change mechanisms are critical for security and accessibility in multi-user Linux systems. I hope this guide gives you a firm grounding on configuring Linux for seamless user switching!