Fullmoon System
Practical lessons from building and operating servers, networks, security systems, and automation.
- 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.