How to Check Whether a User’s Password Is Already Set

1. Overview

In Linux, we use passwords to protect sensitive information and maintain system integrity. As an administrator, ensuring that user passwords are set and secure is important. This helps protect and prevent unauthorized access to our system.

In this tutorial, we’ll explore various methods we can use to check whether a user’s password is already set or not. To begin, we’ll make use of the passwd and chage commands in the command line. Then, we’ll examine the /etc/shadow file. For this to work, we’ll need administrative privileges to execute the commands and examine the file.

2. Using the passwd Command

The passwd command helps us manage user passwords. It allows us to set and update passwords for user accounts. However, we can also use it to check whether a user has a password set:

$ sudo passwd -S samuel
samuel P 07/26/2022 0 99999 7 -1

Above, we use sudo to run the command with superuser privileges. The -S option instructs the passwd command to display the password status of the specified user, which in this case is samuel.

Here, we get an output representing password information for user samuel separated into various fields:

• samuel – represents the user whose password status we’re looking for
• P – indicates that user samuel has a password set
• 07/26/2022 – represents the date the user last changed their password
• 0 – the minimum number of days that must pass before the user can change their password
• 99999 – represents the maximum number of days a password may be used before it must be changed
• 7 – number of days the system will warn the user before their password expires
• -1 – indicates the user account will not be disabled when their password expires

To determine if a user has a password set, we’ll check the value of the second field. A value of P indicates the user has a password set, and a value of NP would indicate that the user has no password set.

From our above output, we have a value of P indicating that user samuel has a password set.

3. Using the chage Command

chage is a Linux command-line tool used to manage and view users’ password aging information. It allows administrators to set password expiration dates and other aging settings. Furthermore, we can use it to check whether a user has a password set:

$ sudo chage -l samuel
Last password change					: Jul 26, 2022
Password expires					: never
Password inactive					: never
Account expires						: never
Minimum number of days between password change		: 0
Maximum number of days between password change		: 99999
Number of days of warning before password expires	: 7

Here, we use the -l option to list the password aging information for user samuel. To check whether a user has a password set, we focus on the Last password change field. If this field contains a date as the output, user samuel has a password set. However, if the output is never, this means the user has not set a password.

4. Examining the /etc/shadow File

/etc/shadow is a Linux file that stores user account information, including password hashes. Moreover, only users with administrative privileges can access the file.

Now, let’s examine the file:

$ sudo cat /etc/shadow
root:!:19199:0:99999:7:::
daemon:*:19101:0:99999:7:::
...
kevin:$y$j9T$iqdMz2kMMMxbeSTzET7Rw/$AfzVfGs9F6f7qRsJy02Ubq/j.EjHMM8ZmQSFlzfsJK2:19590:0:99999:7:::
paul:$y$j9T$3ejQssBdwQKACBEIL2LIz/$bYoGbHUR9Ttf2EUQvb5upj.fMwxErKyLABdDwjt2hzD:19638:0:99999:7:::

In the above example, we use the cat command to print the contents of the /etc/shadow file. Each line in this file represents a different user account with their password information stored in fields separated by a colon.

In this case, to check whether a user has a password set, we’ll examine the second field. If a string of characters representing a hashed password is present in this field, the user has a password set. On the other hand, an asterisk (*) or an exclamation mark (!) means the user has no password set or it’s disabled.

What’s more, we can filter out a specific user from the /etc/shadow file:

$ sudo cat /etc/shadow | grep samuel
samuel:$y$j9T$1jtns/6BZoOju3keIlV9n1$TeUcEKhk.chLTH7DVcJU/OhoxYk2TzF1sX6qRLjJ5K7:19199:0:99999:7:::

Above, we filter out a user named samuel from the /etc/shadow file via the grep command. Here, we see the second field contains a string of characters representing a hashed password. This indicates user samuel has a password set.

5. Conclusion

In this article, we’ve explored different methods for checking whether a user has a password set in Linux. The first method involves checking the password status of a user using the passwd command.

In the second method, we displayed a user’s password aging information using the chage command. Lastly, we examined the /etc/shadow file using the cat and grep commands to list and filter out user information. We can use any of these approaches depending on our preferences.

Ensuring user passwords are set and secure helps maintain system integrity and prevent unauthorized access.