FirewallD
Reference for FirewallD, the dynamic firewall manager for Linux that uses zones and services on top of nftables. Covers zones, services, ports, rich rules, NAT, ICMP filtering, and troubleshooting.
Networking
HTTP Status Codes
Reference for HTTP status codes grouped by class, including standard RFC 9110 codes, common non-standard codes from Nginx and Cloudflare, HTTP/2 and HTTP/3 behavioral notes, and a reverse-proxy troubleshooting table.
IPTables
Reference for the legacy iptables packet-filtering utility: tables, chains, targets, stateful matching, NAT, rule management, and per-distribution persistence. Covers the iptables-nft compatibility layer for modern …
KeepaliveD
Configure Keepalived for high availability on Linux using VRRP and health checks, covering installation, MASTER/BACKUP setup, priorities, IPv6/VRRPv3, notification scripts, and diagnostics.
Mail Server DNS Records
Reference for the DNS records needed to run a mail server: A/AAAA, MX, PTR, SPF, DKIM, DMARC, MTA-STS, ARC, DANE/TLSA, and client autodiscovery.
NetworkManager
Reference for managing wired, wireless, VPN, bond, bridge, and VLAN connections on Linux with NetworkManager via nmcli and nmtui. Covers connection profiles, static and DHCP IP setup, WiFi security, dispatcher scripts, …
NFTables
Reference for the nftables packet filtering framework: address families, tables, chains, rules, sets and maps, NAT, rate limiting, rule management, and migration from iptables.
OpenSSL
Practical OpenSSL reference covering key generation, CSRs, self-signed certificates, inspection, format conversion, OCSP stapling, Certbot, and x509 client authentication with CRLs.
SIP Unified Communication
Reference for the SIP signaling protocol, server infrastructure, codec selection, NAT traversal, trunking, security, and deployment. Covers Asterisk, FreeSWITCH, Kamailio, RTP/RTCP, and messaging-platform bridges.
SMB / Samba
Reference for SMB protocol versions, Samba server installation and share configuration, encryption, VFS modules, performance tuning, audit logging, and client setup on Linux and Windows.