How to List Users in Linux

John on July 04, 2020

Knowing how to list or count users on a Linux system can be very useful for managing who has access to use your server or machine.

What commands can we use to find users and what information can we show about them? In this article, we will go through a number of different commands to list all users and find specific users by their name in Linux.

List All Users from /etc/passwd

All local users are stored in /etc/passwd and can be opened using a command-line based text editor such as nano.

nano /etc/passwd

root:*:0:0:System Administrator:/var/root:/bin/sh
daemon:*:1:1:System Services:/var/root:/usr/bin/false
uucp:*:4:4:Unix to Unix Copy Protocol:/var/spool/uucp:/usr/sbin/uucico
taskgated:*:13:13:Task Gate Daemon:/var/empty:/usr/bin/false
networkd:*:24:24:Network Services:/var/networkd:/usr/bin/false
installassistant:*:25:25:Install Assistant:/var/empty:/usr/bin/false
lp:*:26:26:Printing Services:/var/spool/cups:/usr/bin/false
postfix:*:27:27:Postfix Mail Server:/var/spool/postfix:/usr/bin/false
john:*:1000:1000:John H:/home/john:/bin/bash
james:*:5001:5001:James H:/home/james:/bin/bash

The above output looks messy but once you know what each component of a line represents it is easy enough to break down.

From left to right they are:

• User name
• Encrypted representation of the password
• User ID (UID)
• Group ID (GID)
• Full user name
• User root directory
• Shell default

Pro tip - typically a user with an ID of 1000 and above will be a “real” user and ones below will be “system” users, though there is no physical difference between them.

List Users with Getent

Using the getent command we can get user information from passwd and from the GNU Name Service Switch, which is obtained VIA the /etc/nsswitch.conf configuration file.

getent /etc/paswd

To exit the above output press : (colon) followed by W.

List Users with Compgen

If we just need a list of all users with no other information the compgen command will work perfectly.

compgen -u

root
daemon
bin
sys
...
pollinate
john
-agent
colord

To make the above output easier to look though we can pipe in the sort command to order users alphabetically.

compgen -u | sort

_apt
backup
bin
colours
...
uucp
uuidd
vmail
www-data

Check a User Exists in Linux

If we need to check if a user name exists we can pipe in the grep command to search lines in the user database. If no matches are found nothing will be returned.

getent passwd | grep john

john:x:1000:1000:John,1,,:/home/john:/bin/bash

Note - the above grep command is case sensitive; please follow the above link to the grep command if you would like to learn about how to change the behaviour of grep.

Check Logged in Users in Linux

To check users that are logged into your system use the who command.

who

john     pts/0        2020-07-07 22:18 (82.124.175.9)

Here are the columns of the who command from left to right.

• User name.
• How the user connected; pts/0 for terminal and :0 for GUI (Graphical User Interface).
• Time of log in
• User log in IP address

Conclusion

You now know a number of ways to find out what users have access to your Linux system and what users are logged in. There are other ways to filter down what users by their attributes, though that is more related to the usage of the grep command.