Zip file with English & French PDFs by the ANSSI, the French Cybersecurity Agency (Agence nationale de la sécurité des systèmes d'information)

ANSSI Guidelines - Configuration recommendations of a GNU/Linux System
Guide ANSSI - Recommandations de configuration d'un système GNU/Linux

Version 2.0 (03/10/2022)

Targeted audience: Administrators / IT security managers
Public visé : Administrateur / RSSI

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Configuration recommendations of a gnu/linux system

Unix operating systems and derivatives, including GNU/Linux, are playing an important role in the ecosystem of equipments, systems, networks and telecommunications. They are widely deployed in several equipments. This guide focuses mainly on generic system configuration guidelines and on common sense principles that need to be applied during the deployment of hosted services.

A few configuration rules make it possible to obtain reasonably secure systems as long as some fundamental principles are respected. It should be checked methodologically that these are applied correctly, for example using a checklist.
This guide focuses primarily on generic system configuration guidelines and common sense principles that should be applied when deploying services on a GNU/Linux system.

In particular, the following points are discussed:

General principles of security and hardening
Hardware and firmware configuration
Securing the boot chain
Configuring system services
Kernel configuration
Privilege and access management
Isolation

Source: https://cyber.gouv.fr/en/publications/configuration-recommendations-gnulinux-system