Completed Case Study
Ubuntu Application Server Secure Baseline & Recovery
A Linux infrastructure-security project focused on preparing, hardening, validating, and snapshotting an Ubuntu 24.04 application server before the next cloud-security phase.
Linux Hardening • Firewall • Recovery • Validation
Objective
Prepare wcds-app-01 as a reliable and secure Ubuntu application-server foundation for later cloud-security and hybrid-lab work.
Environment
The lab used Ubuntu 24.04 LTS on VMware Workstation with ADC1 providing AD DS, DNS, and DHCP services, and VMnet8 providing NAT egress for controlled external reachability.
Work performed
Renamed and validated the host, corrected local resolution, repaired package repository trust, simulated and completed a large system upgrade, held Wazuh Manager to preserve scope, repaired GRUB, restricted SSH using UFW, hardened OpenSSH, enabled unattended upgrades, corrected Netplan, and reset failed service state.
Recovery actions
Recovered safely from a GRUB bootloader risk before rebooting, corrected a stale ens33 Netplan definition to match the active ens37 interface, and created VMware recovery snapshots at major change gates.
Validation
Validated hostname persistence, internal DNS, DHCP addressing, default route, Azure HTTPS reachability, kernel boot, package integrity, Wazuh preservation, UFW policy, SSH health, automatic updates, and zero failed systemd units.
Outcome
The server was transformed from a general-purpose Ubuntu VM into a documented, hardened, network-stable application-server baseline with recovery points and clear follow-up recommendations.