Fullmoon System
Practical lessons from building and operating servers, networks, security systems, and automation.
- Preventing AWS Bill Shock: Checking Free Tier, Budget Alerts, and EC2 Charges
If you are on the AWS Free Tier but have been charged, start by checking your sign-up date and account plan. This guide covers setting up AWS Budgets alerts, managing costs for EBS, IPv4, and NAT Gateways that persist after stopping EC2, and the proper cleanup sequence after completing labs.
- VirtualBox and Rocky Linux Installation Troubleshooting
Troubleshooting CPU, UEFI, PXE, installation memory and initramfs issues while installing Rocky Linux 10.2 in VirtualBox.
- Fix No space left on device on Linux: Disk Space, Inodes, and Deleted Files
Diagnose Linux No space left on device errors with df, du, inode checks, lsof, and journalctl, then reclaim space safely.
- How Linux Containers Work: Namespaces, cgroups v2, and Rootless Podman
Understand Linux namespaces, cgroups v2, and OCI image layers, then test isolation, resource limits, security controls, and Quadlet services with rootless Podman.
- Deploy NetBox in an Air-Gapped Network: Rocky Linux 8.10 and Podman
Build a verified offline bundle of RPMs and OCI images, then deploy, secure, back up, and operate NetBox with Podman on Rocky Linux 8.10.
- Python venv Guide: Creation, Activation, requirements.txt, and Production Use
Learn how Python venv works, create and activate environments, manage requirements.txt, deploy offline or with systemd, and remove environments safely.
- Deploy Kubernetes with Kubespray: Rocky Linux 9 and Cilium Operations Guide
Deploy Kubernetes and Cilium with Kubespray 2.31 on Rocky Linux 9, then validate three control-plane nodes, etcd quorum, an API VIP, security, and backups.
- Linux Kernel Architecture: Scheduling, Memory, VFS, Boot, and Troubleshooting
Understand Linux kernel boundaries, scheduling, memory, VFS, and boot, with practical procedures for diagnosing kernel panics and inspecting sysctl safely.
- Deploy Kea DHCP on Rocky Linux 9: Reservations, Validation, and High Availability
Replace end-of-life CentOS 7 and ISC DHCP with Rocky Linux 9 and Kea 3.0 LTS, covering DHCPv4 pools, reservations, logs, firewalls, relays, and HA.
- Kea DDNS with BIND 9: TSIG and Automatic Forward and Reverse DNS Updates
Connect Kea DHCPv4 leases to Kea D2 and BIND 9 using TSIG, forward and reverse zones, DHCID conflict protection, and practical validation.
- Deploy Elastic Stack on Rocky Linux 9: TLS, ILM, and Operations
Install Elastic Stack 9.4.2 on Rocky Linux 9 with security defaults intact, then validate TLS, Kibana, Logstash, Filebeat, ILM, and snapshots.
- OpenLDAP Deployment Guide: cn=config, TLS, ACLs, Backups, and Replication
Operate OpenLDAP 2.6 with cn=config and MDB, validating TLS, least-privilege ACLs, entries, indexes, slapcat backups, restoration, and syncrepl HA.
- DRBD and Pacemaker on Rocky Linux 9: STONITH and Two-Node HA
Build a safe two-node active/passive cluster with DRBD 9, Pacemaker, and Corosync, covering fencing, resource constraints, quorum, and failure tests.
- NetBox with Docker: Pinning 4.6, Security, Backups, and Upgrades
Deploy a compatible NetBox Docker 5.0.1 and NetBox 4.6 stack with Compose, then create an administrator, validate health, back up data and media, and upgrade safely.
- GlusterFS Deployment Guide: Replica 3, Mounting, Healing, and Operations
Prepare storage, configure firewall rules, create and mount a GlusterFS Replica 3 volume, and diagnose healing and split brain with reproducible commands.
- GlusterFS vs. DRBD: Replication, Consistency, and Choosing an HA Design
Compare GlusterFS file replication with DRBD block replication, focusing on concurrent access, consistency, quorum, failover, and operational complexity.
- Practical Ansible Playbooks: Inventory, Idempotency, Vault, and Rolling Deployments
Build safe Ansible workflows with inventories, idempotent tasks, handlers, Vault, preflight checks, recovery, and serial rolling deployments.
- PXE and Kickstart: Unattended Rocky Linux 9 Installation with UEFI
Automate Rocky Linux 9.8 installation with DHCP, UEFI PXE/TFTP, an HTTP installation tree, and a validated Kickstart file.
- Upgrade Rocky Linux 8.8 to 8.10 Safely
Prepare backups, inspect repositories and DNF state, upgrade and reboot, then validate services and establish rollback criteria for Rocky Linux 8.10.
- Migrate CentOS 7 to Rocky Linux 8: A Rebuild-First Guide
Move end-of-life CentOS 7 workloads to Rocky Linux 8.10 through a fresh build, tested backups, selective migration, validation, cutover, and rollback.
- Install Rocky Linux 9.8: UEFI and Initial Security Configuration
Verify the Rocky Linux 9.8 ISO, boot with UEFI, configure LVM, networking, and an administrator account, then update and check the system's security.
- Configure CentOS 7 Vault for EOL Recovery and Migration
Temporarily configure and verify the Vault 7.9.2009 repositories on an end-of-life CentOS 7 server, then migrate to a supported OS.
- CentOS 7.9 Networking: ifcfg, nmcli, and Migration Precautions
Correct static IP configuration with ifcfg and NetworkManager nmcli on CentOS 7.9, protect remote access, and verify, recover, and migrate the server.
- SSH Key Authentication: Ed25519, ssh-agent, and Server Security
Configure SSH public-key authentication with Ed25519 and ssh-agent, verify host fingerprints and permissions, test new sessions, and manage sshd policy and key revocation.
- Open MPI Deployment Guide: Compiling, SSH, Slurm, and Performance Validation
Install Open MPI, use wrapper compilers, align runtimes across nodes, integrate Slurm and PMIx, and validate TCP/UCX, CPU binding, and performance.
- Slurm from Installation to Operations: HPC Resource Management and Job Scheduling
Configure a Slurm cluster with MUNGE authentication, controllers and compute nodes, job accounting, cgroup isolation, and tested backup and recovery procedures.
- Reset a Linux Root Password: Console Access, SELinux, and Audit Procedures
Use authorized console access and rd.break to remount the root filesystem writable, change the password, relabel SELinux files, and verify a normal boot.
- Create a systemd Service: Units, Security, Logs, and Restart Validation
Prepare a dedicated account and executable, register a systemd unit, configure start limits, inspect logs, diagnose failures, and roll back changes.
- Linux Bonding: Mode Differences and CentOS 7.9 Active-Backup Configuration
Compare bonding modes, switch requirements, and bandwidth behavior, then configure, test failover, and roll back active-backup bonding on CentOS 7.9.