How to set user password expirations on Linux

User accounts created on Red Hat Enterprise Linux (RHEL) servers are by default assigned 99,999 days until their password expires. The Center for Internet Security (CIS) provides some advice on controls for hardening systems, and one of these is setting password expirations to 365 days or less. The security team usually enforces this setting, but system administrators must ensure this is done.

Use the /etc/login.defs file to set password aging policies. All new users inherit the definitions set in login.defs. You'll use the chage command to manage password-aging polices.

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In /etc/login.defs, you can adjust the following parameters to reflect your security policy or control:

• PASS_MAX_DAYS: How many days the password is active before it expires.
• PASS_MIN_DAYS: How many days a password must be active before it can be changed by a user.
• PASS_WARN_AGE: The number of days a warning is issued to the user before an impending password expiry.

The following example modifies your policy such that a password expires after 90 days and cannot be changed until it's been active for seven days, and users are notified five days prior to password expiry:

PASS_MAX_DAYS	90
PASS_MIN_DAYS	 7
PASS_WARN_AGE	 5

Changes made to /etc/login.defs affect only new users created on the system. For existing users, you must use the chage command.

You can set the same configuration for existing users with:

$ sudo chage --mindays 7 \
--maxdays 90 --warndays 5 user1

View password age

To view the password age for a user, use the --list option (-l for short) with the chage command. For example, to view password information for user1:

$ sudo chage --list user1
Minimum number of days between password change   : 7
Maximum number of days between password change	 : 90
Number of days of warning before password expires: 5

Password expiry

Use the chage command to set the expiry date for an account. This setting defines a given date, after which a user account is locked and inaccessible. You can do this with the --expiredate (-E for short) option.

For example, to cause the user1 account's password to expire after 90 days, count 90 days forward from the current date (July 15, 2022, in this example):

$ sudo chage -E 2022-07-15 user1

Alternately, use the date command to do a calculation for you:

$ sudo chage --expiredate \
$(date -d +90days +%Y-%m-%d) user1

Password policies

A password policy is one important part of your organization's security posture. With the chage command, you can make your systems manage password reminders and expiry dates reliably. Once the security team defines the appropriate settings, sysadmins can check that the settings are applied consistently.

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