A practical RHEL and Ubuntu hardening plan covering accounts, firewalls, logs, backups and updates. This guide focuses on practical decisions and responsible implementation, not promises of instant results.
Start with an inventory
Write down each Linux server’s owner, operating system, role, public IP exposure and recovery method. A system that nobody owns is difficult to patch safely. Keep the inventory current whenever new services are deployed.
Before touching production, capture a tested backup or snapshot and schedule a change window. A security control is valuable only when it does not accidentally lock administrators out.
Identity and administrative access
Create named administrator accounts and use sudo rather than working routinely as root. Disable unused accounts, rotate leaked keys, limit password authentication where SSH keys and operational policies permit, and enforce multi-factor authentication at the access layer when available.
Check SSH listening interfaces and network access. Avoid direct public exposure when a protected VPN or managed access gateway suits the environment. Never publish a password or private key in an online support ticket.
Firewall, updates and logs
Allow only services the business needs. On RHEL check firewalld zones and rules; on Ubuntu review UFW or nftables as appropriate. Verify that an application remains reachable from approved clients after any firewall change.
Apply vendor-supported security patches and track reboots separately. Review authentication logs, service failures and certificate expiry. Centralized logging helps investigations when a single host becomes unavailable.
Backups and a verification routine
Keep at least one encrypted backup copy separate from the server, establish a retention policy and periodically perform a sample restore. Monitoring a successful backup job without testing restoration is not enough.
A monthly checklist should confirm account access, open ports, disk usage, restore results and recent critical updates. Preserve findings and owner actions in a simple change log.
Always test infrastructure or business-process changes in a controlled environment first. Review your own security, privacy and compliance requirements before going live.