Ytdyklly

As it stated here I consider the simpliest way to discover with -l & -U options together, just type users it will list e.g.: John then:

If the user has sudo access, it will print the level of sudo access for that particular user:

  sudo -l -U John

  User John may run the following commands on this host:

     (ALL : ALL) ALL

If the user don't have sudo access, it will print that a user is not allowed to run sudo on localhost:

   sudo -l -U John

   User John is not allowed to run sudo on localhost.

As it has already been stated, the answer can be found on Unix & Linux Stack Exchange:

This shows that user "saml" is a member of the wheel group.

$ getent group wheel

wheel:x:10:saml

The only difference is that the group in Ubuntu is not wheel, but sudo (or admin in older versions of Ubuntu). So the command becomes:

getent group sudo

Expanding on the sudo -l -U test, one can use getent passwd to determine the users who can use sudo. Using getent allows us to access users who may not be present in the passwd file, such as LDAP users:

getent passwd | cut -f1 -d: | sudo xargs -L1 sudo -l -U | grep -v 'not allowed'

sudo -U does not return a non-zero exit value that we could take advantage of, so we are reduced to grepping the output.

This command returns a list of users with sudo rights:

awk -F ":" '{ system("groups " $1 " | grep -P "[[:space:]]sudo([[:space:]]|$)"") }' /etc/passwd

Output is (e.g.):

<username> : <username> adm cdrom sudo dip plugdev lpadmin sambashare docker

If only the user name to be displayed, then this command:

awk -F ":" '{ system("groups " $1 " | grep -P "[[:space:]]sudo([[:space:]]|$)"") }' | awk -F ":" '{ print $1 }' /etc/passwd

On most Unix-like systems, that have the sudo command, and have a sudo configuration file; running visudo as root:

:~$ sudo bash

or

:~$ su



:~# visudo

will allow an administrator to inspect and amend the privileges of groups that can use the sudo command.

On Debian based Unix-like systems, like Ubuntu, the groups 4 and 27 generally have access rights to the sudo privileges.

Group 4 is the administrator group (adm) and group 27 is the sudo gid.

To see what users are currently assigned to these groups cat the /etc/group file as shown below:

:~$ cat /etc/group

A sample output, on Ubuntu (but not Redhat based, Oracle Solaris/Solaris based, or BSD based systems) would yield this:

adm:x:4:youruser

tty:x:5:

disk:x:6:

lp:x:7:

mail:x:8:

news:x:9: 

uucp:x:10:

man:x:12:

proxy:x:13:

kmem:x:15:

dialout:x:20:

fax:x:21:

voice:x:22:

cdrom:x:24:youruser,mybrother

floppy:x:25:

tape:x:26:

sudo:x:27:youruser,mybrother

As we can tell, youruser is the administrator of the system, and member of
group 4 (adm). But youruser and mybrother are both members of group 27, which is the gid (group identification) number of group sudo. So mybrother can also attain root privileges (super user).

Many linux systems like Fedora and Slackware, incorporate the wheel group gid=10. Which allows administrator privileges when the sudo command is applied. On BSD based systems (e.g. FreeBSD), the root user is a member of the wheel group which is gid 0.

Also by using the id command any user can find the group information of another known user to the system.

For Example:

:~$ id mybrother

Sample output

uid=1001(mybrother) gid=1001(mybrother) groups=1001(mybrother),24(cdrom),27(sudo),30(dip),46(plugdev),108(lpadmin),124(sambashare)

Command -

cat group | grep sudo

Output -

sudo:x:27:Tom,Stacy

Tom,Stacy are the users with sudo privilages