How do I change users in Linux?

Linux
1

I’m trying to switch from my current user to another user in my Linux system. I’m new to Linux and not sure about the right command to use. Can someone assist me with the steps or command to do this? Thanks!

2

To switch between users in a Linux environment, you generally utilize the su (substitute user) or sudo (superuser do) commands, depending on the level of privileges you need and the configuration of your system. Let’s discuss both of these options:

  1. Using su Command:

    • This is probably the most straightforward method if you know the username and password of the target user. Open your terminal and type:

      su - [target_user]

    • Replace [target_user] with the actual username you want to switch to. For example, if you want to switch to a user named john, you would type:

      su - john

    • You’ll be prompted to enter the password for john. If entered correctly, you’ll switch to john's user environment without logging out of the current session.

    • Remember, the - (dash) after su makes sure you load the user’s environment variables, so it’s like a clean login.

  2. Using sudo Command:

    • If you’re in a situation where you want to execute a single command as another user, sudo is quite useful. In some distributions, sudo is preferred because it offers better security control (requiring the user to be in the sudoers group). For instance:

      sudo -u [target_user] [command]

    • To switch to another user interactively using sudo, you can use:

      sudo -i -u [target_user]

    • For example, switching to john interactively would be:

      sudo -i -u john

    • In this case, you’ll be prompted for your password (not john's), assuming you’re authorized in the sudoers file.

  3. Switching to Root User:

    • If you need to switch to the root user specifically (system administrator with all privileges), you can simply do:

      su -

    • Alternatively, if using sudo:

      sudo -i

  4. Changing Shell:

    • If, for some reason, you need to change to another user within a scripting environment and want the same session experience:

      exec su - [target_user]

    • Or:

      exec sudo -u [target_user] -i

    • Using exec replaces the current shell with the one initiated by su or sudo.

  5. Checking Current User:

    • To confirm who you’re logged in as:

      whoami

    • This command outputs the username of the current effective user.

  6. Switch Back:

    • To switch back to your original user, you can type:

      exit

    • Each exit command exits one shell level, so if you’ve switched users multiple times, you might need to type exit several times.

A few tips while managing user switching:

  • Ensure you have the necessary permissions to switch users.
  • If you’re a regular user trying to switch to another user both ways (su and sudo), have the necessary credentials at hand.
  • For administrative tasks, it’s a best practice to use sudo instead of directly logging in as root, to reduce the risk of accidental system-wide changes.

These steps should get you through switching users smoothly. If you face permission issues or command not found errors, double-check if your user is listed in the sudoers file or if su is configured correctly. You can edit the sudoers file safely with the visudo command:

sudo visudo

Insert your user in the correct format to grant the necessary privileges and save the file. Hope this helps, and welcome to the Linux world!

3

Using su or sudo to switch users is generally fine, but it’s not always ideal. su requires knowing the target user’s password, which is a security risk. sudo needs proper configuration in the sudoers file, often a pain.

Better alternatives exist, like using ssh even on your local machine. Yes, ssh! For switching users, try:

ssh [target_user]@localhost

Replace [target_user] with the actual username. Convenient, no need to know the user’s password, as it uses your SSH configuration.

gnome-session in graphical environments lets you switch users more straightforwardly through a user interface, avoiding terminal hassle.

Pros and cons:

Pros of su:

  • Simple for local user switching
  • Loads user’s environment with -

Cons of su:

  • Security risk sharing passwords
  • Not ideal for single command execution without full switch

Pros of sudo:

  • More controlled permissions
  • Executes single commands as another user quickly

Cons of sudo:

  • Needs proper configuration in sudoers file
  • Can become irritating for long sessions

Consider these alternatives to make your life easier. These methods might seem overkill initially, but they’ll save time and trouble in the long run.

4

Hey there @byteguru and @techchizkid covered lots of methods! Honestly, good stuff there, but I think there’s a more modern way to approach this especially if you’re like me, constantly bouncing between a bunch of shells and environments.

I’m a big fan of using terminal multiplexers like tmux or screen to manage multiple user sessions. If these buzzwords sound scary, don’t worry, I’ll break it down. So, here’s why I prefer this approach:

  1. Tmux/Screen Sessions:

    • You can start a Tmux or Screen session, which in essence will hold multiple terminal sessions like tabs in a browser. You can even name these sessions for specific tasks.
    • Once inside a session, you can use su - [target_user] or sudo -i -u [target_user]. The beauty is that you can switch back and forth between different user sessions using simple keyboard shortcuts without exiting.

    For instance:

    tmux new-session -s userSwitch

    Then within tmux:

    su - john
    • Now to switch back to your original user or even another user, you just create another window in tmux, using Ctrl+b then c.

  2. Environment Consistency:

    • You won’t lose any executed command logs, unlike a straight su which kinda sucks for backtracking.

  3. Multiple Sessions:

    • Let’s say you’re testing something as a different user but don’t wanna close your current session. With tmux or screen, you can easily pop between those users without losing your place.
    screen -S userSwitch
su - john

And a bit of my experience—though su and sudo are solid choices, the sudo configuration (aka your sudoers file) can get really finicky. You can mess things up there easily if not careful.

To top it all off, let’s complicate things a tiny bit more—in some situations, especially in server environments, try considering using SSH keys locally, so you could do something like:

ssh [target_user]@localhost

Threading off Byte’s suggestion, setting up SSH keys can streamline things without password prompts all the time. More secure and less hassle.

Oh! And if you’re like me, and easily get lost in a bunch of terminal windows, having a structured tmux session can be a lifesaver. It’s like organizing your messy desk.

And just a nudge of caution, with any of these methods, make sure you are not accidentally doing anything as root without meaning to. Trust me, one rm command error, and you’ll toast the system!

Alright, may not be everyone’s cup of tea but try tmux or screen, might just change your Linux life!