The specific layout is critical for the correct operation of Pluggable Authentication Modules (PAM). Modern systems rarely use the deprecated DES-based scheme.
Shadow File Format System Migration Guide: Key Considerations and Best Practices
Interaction with System Tools. Internal Structure and Fields Each line in the shadow file corresponds to a single user account and is composed of nine fields separated by colons.
8 Account Expiration Date Date when the account is permanently disabled. 5 Maximum Password Age Number of days until the password expires and forces a change.
System Migration Guide for the Shadow File Format
9 Reserved Field Currently unused, reserved for future expansion. File permissions are usually set to -rw-r----- , owned by root with group ownership of shadow or shadow-t.
More About Shadow file format
Looking at Shadow file format from another angle can help expand the discussion and give readers a second clear paragraph under the same section.
More perspective on Shadow file format can make the topic easier to follow by connecting earlier points with a few simple takeaways.
