Today marks the end of my #30DaysLinuxChallenge journey!

I’m closing it out with a practical, security-focused project: building and executing a Linux server hardening and auditing checklist on Red Hat Linux.

This is a perfect combination of RHCSA exam skills + real-world system administration practices.

🎯 Objective

• Apply basic hardening policies
• Configure auditing with auditd
• Create a personal security validation checklist
• Monitor and analyze system logs

📚 RHCSA Skills Covered

✔ User and password security

✔ SELinux & firewall validation

✔ Service management

✔ Log auditing with journalctl and auditd

✔ Shell scripting for checks

📝 Server Hardening Checklist

✅ 1. Set Strong Password Policy

sudo nano /etc/login.defs

Adjust values:
PASS_MAX_DAYS 90
PASS_MIN_DAYS 7
PASS_WARN_AGE 7

✅ 2. Disable Unnecessary Services

sudo systemctl disable --now cups
sudo systemctl disable --now bluetooth

✅ 3. Set File Permissions on Critical Files
ls -l /etc/shadow /etc/passwd /etc/gshadow

✅ 4. Verify SELinux is Enforcing
sestatus
Expected:

SELinux status: enabled
Current mode: enforcing

✅ 5. Harden SSH Configuration

sudo nano /etc/ssh/sshd_config
Recommended settings:

PermitRootLogin no
PasswordAuthentication no
MaxAuthTries 3

Restart SSH:
sudo systemctl restart sshd

✅ 6. Enable and Check Firewall Rules
sudo firewall-cmd --state
sudo firewall-cmd --list-all

✅ 7. Set Up Auditing with auditd
sudo dnf install -y audit
sudo systemctl enable --now auditd

Monitor file access:

sudo auditctl -w /etc/passwd -p wa -k passwd_changes

View audit logs:
sudo ausearch -k passwd_changes

✅ 8. Monitor Logs
sudo journalctl -p err -b

sudo tail -f /var/log/secure

✅ 9. Create a Custom Validation Script (Bonus)
nano ~/server_check.sh

Example:

!/bin/bash

echo "Checking SELinux status:"
sestatus
echo "Checking firewall state:"
firewall-cmd --state
echo "Checking SSH root login setting:"
grep PermitRootLogin /etc/ssh/sshd_config

Make executable:
chmod +x ~/server_check.sh

Run:
./server_check.sh

✅ Recap

🎉 Why This Matters

This project combined almost every core RHCSA skill:

• Service & user management
• SELinux & firewall security
• System auditing
• Scripting and automation

In the real world, this is the starting point of any secure Red Hat deployment.