2 Prerequisites This skill 0 Unlocked

Skill · Linux · Harden a Linux server against a baseline

Harden a server's access and privileges: SSH, PAM, sudo, permissions and scheduling

Restrict access to a server: hardened sshd, account lockout with PAM, logged sudo, sensitive permissions fixed and scheduling limited to authorized accounts.

Start lesson 1The Linux domain

• 5 lessons
• ~2 h 05 of reading
• 5 quizzes
• 0 proof lab

The path

Where it comes from, where it leads

What you need to know first, where you stand on this skill, and what it opens next. Your status is computed in your browser, from what you have read and passed.

Before · 2 prerequisites

• Access a machine over SSH
• Manage users, permissions and processes

Recommended before · 2

• Manage a server's accounts and delegation: users, groups, LDAP directory, sudo and ACLs
• Automate in the shell and schedule tasks

This skill, for you

Harden a server's access and privileges: SSH, PAM, sudo, permissions and scheduling

Computing

It unlocks · nothing yet

No other skill requires it: it is an end-of-path skill.

Lessons

How to learn it

5 lessons, about ~2 h 05, in program order. Each lesson ends with its quiz.

The program

5 lessons · ~2 h 05

1. 1Durcir l'accès SSH (in French)· 25 min
2. 2Durcir l'authentification avec PAM (in French)· 25 min
3. 3Durcir et journaliser sudo (sudoers) (in French)· 20 min
4. 4File permissions and ownership: harden a Linux system· 40 min
5. 5Restreindre cron et at : maîtriser qui planifie des tâches (in French)· 15 min

Beyond the lessons

Assess, practise, pass the proof

Reading a lesson confirms nothing. A skill is confirmed by a passed quiz, practised in a guided lab, and put to the test by a challenge or a mission; an imported lab result is not verified by the site.

Assess yourself

5 quizzes

At the end of the lessons: passed at 70%, they confirm the skill.

Practice

1 guided lab

• Set up a collaborative directory with the set-GID bit

Proof

No proof

Neither a challenge nor a mission with a proof yet.

Around it

Who requires it, who teaches it

Required by

• Linux Administrator
• RHCSA (EX200, RHEL 10)

In red: the certification it prepares for.

Taught by

• Durcissement Linux (in French)

Same block · Harden a Linux server against a baseline

• Measure a server's gap to a hardening baseline and prioritize the measures (ANSSI-BP-028, CIS)
• Harden boot, mounts and the local session: GRUB, nodev, nosuid, noexec, banners, dconf
• Harden the running kernel: persistent sysctl parameters and blocked modules
• Confine a service: mandatory access control (SELinux or AppArmor), then systemd sandboxing
• Trace who did what on a Linux server with auditd: persistent rules, ausearch and aureport
• Rebuild a KSPP-hardened kernel and prove its options at boot
• Harden a NixOS server declaratively: versioned measures, test before switching, runtime checks and rollback to a healthy generation

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