AUTH-9216 - Consistency of password/group files

This information is provided as part of the Lynis community project. It is related to Lynis control AUTH-9216 and should be considered as-is and without guarantees. Any advice and commands should be tested before implementing them in production environments.

Control details


The password and group files (and their shadow equivalents) are an important part in the authentication process. Also the security controls like access control and file permissions are impacted by proper authentication and accounting of users. Inconsistencies in the password file can be caused by malicious activities or in some cases due to improper usage of tools, like a file editor. Inconsistencies should therefore be checked and fixed.

How to solve

Run a tool like grpck to detect issues in password and group files. See the man page on your platform, before running this command. Our advice is to check first in read-only mode, before applying any changes. This way the cause can be determined, why inconsistencies showed up in the first place.

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Lynis is a technical security auditing tool for Unix flavors like Linux, macOS, AIX, Solaris, and *BSD. It is open source software and free to use. Typical usage include system hardening, compliance testing, and vulnerability scanning. The project has an active community, including development via GitHub.

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