How To Change Users In Linux – Linux User Account Switching

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Switching between users in Linux is done with a simple command to access different accounts. Understanding how to change users in linux is essential for system administrators, developers, and anyone sharing a computer. This guide covers every method, from basic commands to advanced tricks, ensuring you can switch users efficiently and securely.

Linux offers multiple ways to change users, each suited for different scenarios. Whether you need to run a single command as another user or fully log into a different account, the process is straightforward. Let’s start with the most common method.

Using The Su Command To Switch Users

The su (substitute user) command is the traditional way to change users in Linux. It allows you to switch to any user account, provided you have the password.

To switch to another user, open a terminal and type:

su - username

The hyphen (-) is crucial. It creates a login shell, loading the target user’s environment variables and home directory. Without it, you stay in your current environment.

Switching To The Root User

To become the root user (superuser), simply type:

su -

Or:

su - root

You’ll be prompted for the root password. Once entered, your prompt changes to #, indicating root privileges.

Running A Single Command As Another User

Sometimes you only need to execute one command as another user. Use the -c option:

su - username -c "command"

For example, to list files in another user’s home directory:

su - jane -c "ls -la /home/jane"

This runs the command and returns you to your original shell.

Exiting A User Session

To return to your original user, type exit or press Ctrl+D. This closes the su session.

Common issues with su:

  • Forgotten password: You need the target user’s password, not your own
  • No hyphen: Environment variables may not load correctly
  • Permission denied: Ensure the target user exists and has a valid shell

Using The Sudo Command For User Switching

The sudo command offers more control and security. It allows authorized users to run commands as another user, typically root, without needing the target user’s password.

Running Commands As Another User With Sudo

The basic syntax is:

sudo -u username command

For instance, to create a file as user “bob”:

sudo -u bob touch /home/bob/newfile.txt

You’ll be prompted for your own password (not bob’s). This is a key security feature.

Switching To A User Shell With Sudo

To start a shell as another user:

sudo -u username -i

The -i flag simulates an initial login, loading the user’s environment. Alternatively:

sudo -u username -s

This starts a shell without changing the environment.

Switching To Root With Sudo

To become root:

sudo -i

Or:

sudo su -

The latter combines sudo and su, a common pattern for gaining root access.

Sudo Configuration With Visudo

The /etc/sudoers file controls who can use sudo. Always edit it with visudo to prevent syntax errors:

sudo visudo

Common configurations:

  • Allow a user to run commands as any user: username ALL=(ALL:ALL) ALL
  • Allow a group: %groupname ALL=(ALL:ALL) ALL
  • Allow passwordless sudo: username ALL=(ALL) NOPASSWD: ALL

How To Change Users In Linux Using Graphical Interface

Not everyone prefers the command line. Linux desktop environments offer graphical methods to switch users.

Using The System Menu

Most desktop environments (GNOME, KDE, Xfce) have a user switch option:

  1. Click the system menu (top-right corner)
  2. Select “Switch User” or “Log Out”
  3. Choose another user from the login screen
  4. Enter their password

This keeps your original session running in the background.

Using The Lock Screen

Press Super+L (Windows key + L) to lock the screen. Then click “Switch User” on the lock screen.

Fast User Switching

Some distributions support fast user switching, allowing multiple users to be logged in simultaneously. This is common in Ubuntu, Fedora, and Linux Mint.

Using The Login Command For Direct User Change

The login command is a low-level method. It’s rarely used directly but appears in scripts and recovery scenarios.

To switch users with login:

sudo login username

This prompts for the user’s password and starts a new login session. It’s similar to su - but more primitive.

Using The Ssh Command For Remote User Switching

If you’re managing a remote server, SSH allows you to change users after connecting.

Connecting As A Different User

Specify the user at connection time:

ssh username@hostname

For example:

ssh jane@192.168.1.100

You’ll be prompted for jane’s password.

Switching Users After SSH Login

Once connected, use su or sudo as normal. This is common for accessing root privileges on remote systems.

Managing User Sessions And Processes

When you switch users, understanding sessions and processes is important.

Checking Current User

Use whoami or id to verify your current user:

whoami
id

Listing Logged-In Users

The who and w commands show all active users:

who
w

This helps identify which users are currently using the system.

Running Processes As Another User

To start a background process as another user:

sudo -u username nohup command &

This keeps the process running even after you log out.

Security Considerations When Changing Users

Changing users carries security implications. Follow these best practices.

Use Sudo Instead Of Su When Possible

Sudo provides auditing and fine-grained permissions. All sudo commands are logged in /var/log/auth.log or /var/log/secure.

Avoid Sharing Passwords

Never share passwords between users. Use sudo with appropriate permissions instead.

Limit Root Access

Only grant root access to trusted users. Use groups and sudo rules to restrict commands.

Log Out After Use

Always exit user sessions when done. Leaving a root shell open is a security risk.

Troubleshooting Common User Switching Issues

Even experienced users encounter problems. Here are solutions to frequent issues.

Permission Denied Errors

If you get “Permission denied” when using su or sudo:

  • Check if the user exists: id username
  • Verify the user has a valid shell in /etc/passwd
  • Ensure you’re in the sudoers file (for sudo)

Authentication Failure

If authentication fails:

  • Double-check the password (remember, su uses the target user’s password)
  • For sudo, use your own password
  • Check if the account is locked: sudo passwd -S username

Environment Variables Not Loading

If environment variables don’t load after switching users:

  • Use the hyphen with su: su - username
  • Use -i with sudo: sudo -u username -i
  • Manually source profile files: source ~/.bashrc

Cannot Switch To Root

If you can’t switch to root:

  • Ensure root account is enabled: sudo passwd root
  • Use sudo instead: sudo -i
  • Check if root login is restricted in /etc/ssh/sshd_config (for remote)

Advanced User Switching Techniques

For power users, these techniques offer more flexibility.

Using Su With Environment Variables

Preserve specific environment variables when switching users:

su - username -c "export VAR=value; command"

Switching Users In Scripts

In bash scripts, use sudo -u to run commands as another user:

#!/bin/bash
sudo -u www-data php /var/www/script.php

Using The Runuser Command

Some distributions include runuser, similar to su but for service accounts:

runuser -l username -c 'command'

Creating Aliases For Frequent Switches

Add aliases to your .bashrc for common switches:

alias tojane='sudo -u jane -i'
alias toroot='sudo -i'

Comparing User Switching Methods

Here’s a quick comparison of the main methods:

Method Requires Password Loads Environment Best For
su – Target user’s Yes Full user switch
sudo -u Your own With -i flag Single commands
sudo -i Your own Yes Root shell
Graphical Target user’s Yes Desktop users
SSH Target user’s Yes Remote access

Best Practices For User Management

Effective user management goes beyond switching. Follow these practices.

Use Groups For Permission Management

Instead of switching users, add users to groups:

sudo usermod -aG groupname username

Implement Sudo Rules Carefully

Grant minimal necessary permissions. Use command-specific sudo rules:

username ALL=(ALL) /usr/bin/systemctl, /usr/bin/journalctl

Regularly Audit User Activity

Check logs for unusual user switches:

sudo grep 'su\|sudo' /var/log/auth.log

Disable Unused User Accounts

Lock accounts that are no longer needed:

sudo usermod -L username

How To Change Users In Linux On Different Distributions

While the commands are similar, some distributions have quirks.

Ubuntu And Debian

Ubuntu disables the root account by default. Use sudo for all administrative tasks. To enable root:

sudo passwd root

Fedora And Red Hat

Fedora uses sudo but also allows direct root login. The wheel group grants sudo access:

sudo usermod -aG wheel username

Arch Linux

Arch requires manual sudo configuration. Install sudo and edit /etc/sudoers with visudo.

OpenSUSE

OpenSUSE uses sudo similarly. The sudo group is pre-configured.

Automating User Switching With Scripts

For repetitive tasks, automate user switching.

Simple Script To Run Commands As Another User

#!/bin/bash
# run_as_user.sh
if [ $# -lt 2 ]; then
    echo "Usage: $0 username command"
    exit 1
fi
sudo -u "$1" "${@:2}"

Script To Switch Users And Execute Multiple Commands

#!/bin/bash
sudo -u jane bash -c '
    cd /home/jane
    ls -la
    echo "Running as jane"
'

Understanding User IDs And Groups

Linux identifies users by numeric IDs. Understanding this helps with switching.

Viewing User And Group IDs

Use id to see all IDs:

id username

Output shows UID (user ID), GID (primary group ID), and supplementary groups.

Switching By UID

You can switch users by UID:

su - $(id -un 1001)

This switches to the user with UID 1001.

Common Mistakes When Changing Users

Avoid these frequent errors.

Forgetting The Hyphen With Su

Without the hyphen, environment variables don’t load. This causes path issues and missing aliases.

Using Sudo Without Proper Configuration

If sudo isn’t configured, you’ll get “user is not in the sudoers file.” Fix this by adding the user to the sudo group.

Staying In Root Shell

Forgetting to exit root shells can lead to accidental system changes. Always type exit when done.

Mixing Up Passwords

Remember: su requires the target user’s password; sudo requires your password.

Frequently Asked Questions

What Is The Difference Between Su And Sudo?

Su switches to another user and requires that user’s password. Sudo runs commands as another user using your own password, with permissions defined in /etc/sudoers.

Can I Change Users Without A Password?

Yes, if you have sudo access configured with NOPASSWD in /etc/sudoers. You can also use su if you know the target user’s password.

How Do I Switch To Root User In Linux?

Use sudo -i or su -. On Ubuntu, use sudo -i since the root account is disabled by default.

What Command Shows The Current User In Linux?

Use whoami or id. The who command shows all logged-in users.

How To Change Users In Linux Without Logging Out?

Use