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I'd like to log in as a different user without logging out of the current one (on the same terminal). How do I do that?

tshepang
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    I asked a similar question, because I ran into issues with XDG environment variables ($XDG_RUNTIME_DIR in particular) that were driving me nuts. -> http://unix.stackexchange.com/questions/354826/how-to-switch-between-users-on-one-terminal-completely-xdg-environment-variab – Jonathan Komar Mar 30 '17 at 14:07

10 Answers10

875

How about using the su command?

$ whoami
user1
$ su - user2
Password:
$ whoami
user2
$ exit
logout

If you want to log in as root, there's no need to specify username:

$ whoami
user1
$ su -
Password:
$ whoami
root
$ exit
logout

Generally, you can use sudo to launch a new shell as the user you want; the -u flag lets you specify the username you want:

$ whoami
user1
$ sudo -u user2 zsh
$ whoami
user2

There are more circuitous ways if you don't have sudo access, like ssh username@localhost, but sudo is probably simplest, provided that it's installed and you have permission to use it.

tshepang
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Pratt
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    Also, su - [user] may be useful -- the extra dash gives you a login shell. – ephemient Oct 27 '10 at 20:40
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    I am getting this error "-su: /dev/stderr: Permission denied" after executing this command echo >>/dev/stderr on a login with su --login ..., any tip? I found this btw http://unix.stackexchange.com/questions/38538/bash-dev-stderr-permission-denied – Aquarius Power Nov 24 '14 at 18:58
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    Does this allow each new user to have different, overriding values for environment variables? e.g. git config for work, open source, etc. – Kevin Suttle Dec 23 '15 at 21:13
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    One finding, when I listed the env it saw that everything was in order as well as a visual inspection can go; And one thing was incorrect: XAUTHORITY=/home/user1/.Xauthority'. Not sure _why_? So X-window doesn't work by default because the protection on~/.Xauthorityfile is:-rw-------`. I made a copy and that let me run gedit as an experiment. – will Dec 26 '15 at 11:47
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    if you get "This account is currently not available": su -s /bin/bash - www-data – max4ever Mar 15 '19 at 12:19
  • I am slightly off the topic, but mentioning this in case you or someone else can use it. Assuming that you are using a modern OS and have tmux installed (or can install it), one way would be to:
    1. Login to the host.
    2. Launch a tmux or screen session.
    3. Split the pane or open one or more windows as needed.
    4. Sudo as the other user as mentioned by others here.
    5. Switch back and forth between the users. You need not logout of any session to switch users.

    Please lookup tmux for shortcuts that can help you save a lot of time.HTH.

     – Hopping Bunny Mar 20 '19 at 04:46
  • Worth noting: while sudo -u user … works fine on Archlnux, however on Ubuntu 18.04. It gives the wrong home directory, e.g. echo ~ gives root dir for me. Using su - user works fine however. – Hi-Angel May 27 '20 at 14:23
67

Generally you use sudo to launch a new shell as the user you want; the -u flag lets you specify the username you want:

[mrozekma@etudes-1 ~] % whoami
mrozekma
[mrozekma@etudes-1 ~] % sudo -u nobody zsh
[nobody@etudes-1 ~] % whoami
nobody

There are more circuitous ways if you don't have sudo access, like ssh username@localhost, but I think sudo is probably simplest if it's installed and you have permission to use it

Michael Mrozek
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$ whoami

This command prints the current user. To change users, we will have to use this command (followed by the user's password):

$ su secondUser
Password:

After entering the correct password, you will be logged in as the specified user (which you can check by rerunning whoami.

HalosGhost
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Ashish Saini
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34

If you're running Ubuntu, and if the user you want to login as doesn't have a password set:

sudo su - username

Enter your own password and you should be set. Of course, this requires that your user has rights to gain root privileges with sudo.

Sundae
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To switch the terminal session to a different user, where that user can't exit back into the original user, use exec:

$|# exec su - [username]

This will technically login the new user in a new term process, and close out the current one. That way when the user attempts exit or Ctrl-D, the terminal will close as though that user was the one who instantiated it, i.e., the user can't exit back into the original user's term. Kind of pointless, considering they can still just start a new terminal session and automatically be in the original user term login, but there it is.

EDIT: For what it's worth, you can use linux vlock command in your ~/.bashrc to lock terminal sessions by default, requiring the password of the term session user to unlock. This would somewhat prevent the aforementioned term restart under the original user context, given the term isn't instantiated using the non-default ~/.bashrc of the user, as configured.

SYANiDE
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    Using exec is a good use-case when you are on an SSH-connection, and want to "hand" an existing connection to another user without the need to reconnect. I wonder if there are vulnerabilities in terms of security with regard to this. – Yeti Jan 05 '20 at 21:12
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    It's a direct process fork; nothing should be inherited by the new process... except environment variables and path! Oh, and potentially also ssh-agent. Envars and ssh-agent keyring could be worrisome! – SYANiDE Jan 13 '20 at 21:18
6

sudo -iu <your_username> for me do the trick

andilabs
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3

Yet another route is to launch a new shell as a different (non-root) user to run commands as that user. 

ubuntu@aws-ip:~$ sudo -u mongodb bash          #<-- or zsh, etc... 
mongodb@aws-ip:~$ mongod --configsvr --dbpath /data/configdb --fork

An example of this is the mongodb user. When deploying a sharded MongoDB cluster, all the necessary processes must run as mongodb and it's not necessary (or entirely convenient) to daemonize the processes using init scripts for dozens of nodes.

4Z4T4R
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3

Let us get this right: You are logged in as UserA and want to "login" as UserB to run some commands, but would like to come back to UserA when done. For the sake of simplicity, I assume that you want to run ls -l /tmp as UserB. If you do not want to leave the current shell of UserA but rather run a command as UserB and still remain logged in as UserA, you should do this:

su - UserB -c "ls -l /tmp"   <-- Just an example

This assumes you know the password for UserB. However, if you do not know UserB's password, you need to know the root password. Then:

sudo su - UserB -c "ls -l /tmp"   <-- UserB's pw not needed here

If you would rather temporarily login as UserB to run lots of commands, then just do:

sudo su - UserB

This will give you a new shell for UserB (check that by typing id). When done, you can do ctrl-d and return to your login.

Hopping Bunny
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1

If you need to run just a single command, you can use sudo: sudo -u username command

Maksim Luzik
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-1
~$ sudo login

Then it will prompt you for the sudo password (the currently logged in user's password).

Also: make sure that the current user is in the sudoers file!

Minix
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Tshepo
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