How to switch user in Linux?

Linux
1

I’m currently logged into my Linux system as one user, but I need to switch to another user for a specific task. I’m not sure of the exact command to do this. Can someone guide me on how to switch users in Linux? Thanks!

2

You’re asking about switching users in Linux? Really? This isn’t rocket science. You’d think someone dealing with Linux would know the basics. Anyway, just use the su command. Simple type su - <username> and it’ll prompt you for the password. If you dn’t know the password, guess what? You’re stuck unless you can get the password from whoever manages the accounts.

Pros of su? It’s straightforward and doesn’t require any fancy tricks. But on the downside, let’s be real, it’s not the most secure method. You’re giving full access to another user, which can be a risk if they screw something up.

If you want to switch back to your original user, just type exit or logout. The alternative is sudo -i <command> if you’re only needing to run specific commands as another user without fully switching. But hey, if security isn’t your thing, why even bother worrying?

Competitors? Maybe SSH into another session as a different user, but without the right keys that’s a pain too. At the end of the day, stop asking such basic stuff. Googling around might actually be quicker than posting in forums.

3

It’s fine if you’re a bit unsure about how to switch users in Linux; we all start somewhere. Though @techchizkid gave a pretty… direct… response, I’ll try to clarify and expand on the options for you.

What you’re looking for can be done in a few different ways:

Simple User Switch with su

  1. Using su (Substitute User):

    su - <username>

    This command will substitute the current user with the user specified. You’ll need to know the password of the target user. You’ll be dropped into their home directory, which might be useful depending on what you need to do. To return to the original user, just type exit or logout.

  2. Using sudo:
    sudo is more commonly used for running commands with superuser privileges, but you can also switch users:

    sudo -u <username> -s

    This will start a shell as the specified user. You might need sudo permissions to do this, though.

  3. sudo for single commands:
    If you just need to run a specific command as another user:

    sudo -u <username> <command>

    This is a bit more secure than switching completely, as it limits your interaction to just that command.

Advanced Methods

  1. Using ssh for Remote Switching:
    If you have SSH configured, you might find it handy to just login as the user you need for your task. However, this assumes the different user accounts are set up on the same machine or accessible over the network:

    ssh <username>@localhost

    This method is particularly useful for performing tasks that you want contained within a single secured shell session.

  2. Graphical User Interfaces:
    In case you are using a graphical interface, many DEs (Desktop Environments) like GNOME or KDE provide options to switch users without logging the other user out. This can be found in the system menus, often under “Switch User” or similar.

Security Concerns to Consider

Let’s sprinkle a bit of security mindfulness:

  • su vs sudo: The su command effectively gives the new user every permission the original user has. On the other hand, sudo can be confined to specific commands, which is inherently more secure.

  • Account Management: If you find yourself frequently needing to switch users for specific tasks, it might make sense to reconsider how permissions and roles are managed in your system. Linux systems shine when it comes to fine-grained permission controls—make use of them!

  • Auditability: By using sudo, many systems are set up to log the commands executed, which is useful for auditing what happened on the server, especially in multi-user environments.

Practical Advice

  • Script It: If you frequently need to execute a series of commands as another user, consider scripting them with either an su or sudo wrapper. This can save a lot of typing and reduce manual errors:

    #!/bin/bash
sudo -u <username> <<'EOF'
whoami
# Your commands here
EOF

  • Avoid Root: Never make a habit of operating as root unless absolutely necessary. The root user has unrestricted access to everything on the system, and it’s best to elevate privileges only when needed.

User Switching Etiquette

While it’s perfectly valid to switch users for specific tasks, remember that maintaining a clean and minimalistic permission setup is often more manageable in the long term. If tasks are repetitive and cross user boundaries, it’s a sign you might need to revisit how access controls are configured.

So, while @techchizkid mentions that googling basics might be quicker, there’s real value in community discussions. They often provide context and varied experiences you won’t always find in a straightforward search result.

Feel free to ask more questions if you need further help or clarification!

4

First off, kudos to @techchizkid and @byteguru for laying out the essentials. But listen, let’s mix it up a bit and add some flavor to the conversation.

If you’re all about multitasking and speed, have you ever considered screen or tmux sessions? They might just be the game-changer you didn’t know you needed. Think of it like having multiple tabs in your terminal, but way cooler.

Using screen or tmux

  1. Install screen or tmux:
    If you’re not already using one, install it with:

    sudo apt-get install screen
# or
sudo apt-get install tmux

  2. Start a new session for each user:
    Open a new screen or tmux session and switch users there. For screen:

    screen -S <session_name>
su - <username>

    For tmux:

    tmux new -s <session_name>
su - <username>

  3. Switch between sessions easily:
    This way, you can quickly switch between different user sessions without logging in and out. In screen, switch using:

    screen -list
screen -r <session_name>

    In tmux, switch with:

    tmux ls
tmux attach-session -t <session_name>

This approach is especially handy if you juggle multiple user tasks frequently. Seriously, imagine the time saved!

Security with su and sudo

I see a lot of talk about su vs sudo security. It’s worth noting that both have their place but differ greatly in their methodology. Sudo is definitely the preferred tool for running specific commands due to its logging capabilities. For instance:

sudo -u <username> <command>

Using sudo for individual commands keeps things tighter and more controlled. For extensive tasks, though, a full user switch might still be ideal.

Case in Point

Consider a hypothetical system admin named Steve. Steve uses screen to maintain sessions as multiple users: root, admin, and dev. This setup allows Steve to manage server configurations, user permissions, and application deployments concurrently without constantly typing passwords. Imagine Steve’s productivity skyrocketing while maintaining robust security and minimal risk of cross-contamination errors.

Advanced Tip with ssh

If you manage remote servers or multiple local user accounts, an underused yet highly effective trick is setting up passwordless SSH (with key-based auth) for seamless user transitions:

ssh-keygen -t rsa
ssh-copy-id <username>@<hostname>
ssh <username>@<hostname>

This technique can also work locally (localhost) and saves a ton of time!

Final Thoughts

Ultimately, balancing agility with security is key. For quick and dirty tasks, su - <username> or sudo -u <username> -s might suffice. But if you’re managing a server farm or switching constantly, tools like tmux or screen can be invaluable.

Don’t stress too much about asking basic questions—better to ask and learn than to be ignorant and screw something up, right? We’ve all been there. Try out different methods and see what fits your workflow best. Good luck!