A good Linux administrator must know how many super users and normal users are there in a system he is managing. However, there are chances that sometimes we need to give a temporary sudo access to a normal user to install a software or do certain administrative task on his/her own. Over time, we might forget to revoke the sudo privileges. So, it is good practice to know how many super users are in your Linux system from time to time. If there are any forgotten or unwanted sudo access, you can simply revoke them. This brief guide explains how to find all sudo users in Linux.

Find All Sudo Users In Linux

Let us first list all users in the system. To do so, run:

$ awk -F':' '{ print $1}' /etc/passwd

Sample output from my Ubuntu system:

root
daemon
bin
sys
sync
games
man
lp
mail
news
uucp
proxy
www-data
backup
list
irc
gnats
nobody
systemd-timesync
systemd-network
systemd-resolve
systemd-bus-proxy
syslog
_apt
lxd
messagebus
uuidd
dnsmasq
sshd
sk
senthil
kumar
ostechnix

You can also use the following command to list all users:

$ compgen -u

Among all users, let us only find the sudo or super users in our Linux system.

$ grep '^sudo:.*$' /etc/group | cut -d: -f4
sk,ostechnix

Also, you can use “getent” command instead of “grep” to get the same result.

$ getent group sudo | cut -d: -f4
sk,ostechnix

As you see in the above output, “sk” and “ostechnix” are the sudo users in my system.

In the above examples, we listed all sudo users. You might want to know whether a certain user has sudo privilege or not.

To do so, run:

$ sudo -l -U sk

Sample output:

Matching Defaults entries for sk on ubuntuserver:
 env_reset, mail_badpass,
 secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin

User sk may run the following commands on ubuntuserver:
 (ALL : ALL) ALL

As you see, the user named “sk” can perform all commands. So, he is in the sudo group.

Let us check another user.

$ sudo -l -U senthil

Sample output:

User senthil is not allowed to run sudo on ubuntuserver.

Oops! The user “senthil” is not allowed to run sudo, so he is just a normal user.

We can also find if an user has sudo access by running the following command:

$ sudo -nv

If you get nothing as output, the user still has sudo access.

If you see an output like below, then the user doesn’t has sudo access.

$ sudo -nv
Sorry, user senthil may not run sudo on ubuntuserver.

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Suggested read:

• How To Grant And Remove Sudo Privileges To Users On Ubuntu
• How To Restore Sudo Privileges To A User
• How To Run Particular Commands Without Sudo Password In Linux
• How to force users to use root password instead of their own password when using sudo

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