oikos/containers/107-dns.md

107 — dns

Homelab DNS server (Technitium). Replaces the dnsmasq that lived on 124 — authentik; single-purpose, one job.

At a glance

• Hostname: dns
• IP: 192.168.8.2 (static — stable, decoupled from any app)
• Privilege: privileged (Docker-in-LXC, features: nesting=1)
• Resources: 1 core / 1 GiB / 8 GiB rootfs
• Created: 2026-06-01, Debian 13. Its own resolver is 1.1.1.1 (no circular dependency on the DNS it serves).

Role

Authoritative split-horizon DNS for hubris.network on the LAN/mesh, plus recursive forwarding (1.1.1.1, 8.8.8.8) for everything else. Technitium runs in Docker (technitium/dns-server:latest, network_mode: host), web console on :5380.

The hubris.network zone

• Specific A overrides: app names → 192.168.8.175 (Caddy), nfs-export → 192.168.8.200, auth/sso/... as needed.
• auth.hubris.network → 82.165.190.79 (VPS Authentik), sso.hubris.network → 192.168.8.175 (LAN forward-auth outpost).
• Wildcard *.hubris.network → 82.165.190.79 — mirrors the public IONOS wildcard so undefined names (e.g. netbird) resolve to the VPS, matching public behaviour.
• MX / SPF-TXT / CAA replicated from public so an authoritative zone doesn't shadow hubris.network email/cert records.

Config / access

• /opt/technitium/docker-compose.yml; admin password in /opt/technitium/admin_password.txt (mode 600 — sops-encrypt in Phase 5).
• Console: http://192.168.8.2:5380 (user admin).
• API: http://192.168.8.2:5380/api/... (token via /api/user/login). Zone was built via the API.

Who points here

• NetBird mesh peers: resolve via the NetBird managed DNS zone, kept in sync from this Technitium (see dns-sync below). The home-lab-dns nameserver group (→ 192.168.8.2) is a thin fallback forwarder.
• Homelab DHCP clients: Technitium's own DHCP scope hands out 192.168.8.2 as the DNS server for 192.168.8.x leases (see DHCP section below).
• Plain LAN clients (192.168.178.x): Fritz!Box DHCP still hands out Fritz!Box itself (192.168.178.1) as DNS — no split-horizon for non-mesh clients. Changing this requires a secondary DNS fallback, which Fritz!OS 8.x doesn't expose in a single DHCP field.

dns-sync (Technitium = authoring source)

/opt/dns-sync/sync.py (cron */10, logs /var/log/dns-sync.log) reconciles this zone's named A-records → the NetBird managed DNS zone via the NetBird API (/api/dns/zones/{id}/records). Token at /opt/dns-sync/netbird-token (mode 600; source of truth in sops secrets/netbird-pat.yaml). Edit DNS only here; the sync propagates to the mesh. It deletes NetBird records absent from Technitium. Tracked: scripts/dns-sync.py. Why this exists: NetBird won't forward to Technitium for mesh peers (self-IP / nameserver-group quirks), so we sync into the managed zone instead — see dns.md.

DHCP

Technitium also runs a DHCP server for the homelab subnet (enabled 2026-06-02):

• Scope: homelab — 192.168.8.241 – 192.168.8.254
• Gateway: 192.168.8.1 (Proxmox vmbr0 alias)
• DNS: 192.168.8.2 (self)
• Lease time: 24 h

Replaces the DHCP that was previously served by the Slate AX router. Static-IP LXCs (.101–.239) are excluded from the pool. Pool narrowed from .100–.240 to .241–.254 on 2026-06-03 to eliminate IP conflict risk.

Related

• 124 — authentik — retired host of the old dnsmasq
• DNS split-horizon
• Mesh

Changelog

2026-06-24 — A record trmnl.hubris.network → 192.168.8.175

Added for trmnl (128) (LAN path via Caddy (121)); propagated to the NetBird managed zone by dns-sync.

2026-06-06 — dns-sync cron installed (had been missing since deployment)

Although the 2026-06-03 changelog claimed "cron */10", no crontab was actually configured on the LXC. The sync was running only via ad-hoc manual invocations during incident debugging. Fixed by adding /etc/cron.d/dns-sync.

2026-06-03 — DHCP pool narrowed to .241–.254

Previous pool .100–.240 overlapped with all static LXCs/VMs (.101–.239). Shrunk via API (/api/dhcp/scopes/set). 11 stale DHCP leases in .101–.110 remain until natural expiry (2026-06-04). See plan.

2026-06-03 — dns-sync added (Technitium → NetBird managed zone)

This Technitium became the single DNS authoring source; /opt/dns-sync/sync.py (cron */10) reconciles named A-records into the NetBird managed zone via the API. Fixed previously-broken mesh names (sso, nfs-export, mcp, secrets) by adding them to the managed zone; reaped obsolete files/photos-new. See dns.md.

2026-06-02 — DHCP server enabled; replaces Slate AX DHCP

Enabled Technitium's built-in DHCP server for 192.168.8.0/24 (scope homelab, range .100–.240, gateway 192.168.8.1, DNS self). Previously the Slate AX sub-router served DHCP for the homelab subnet. With the Slate AX retired and Proxmox now the subnet router, Technitium takes over DHCP. Configured via the Technitium API (/api/dhcp/scopes/set). DHCP LXCs kept their Slate AX leases until expiry, then renewed from Technitium.

2026-06-01 — created; replaced dnsmasq on 124

Stood up Technitium at 192.168.8.2, imported the split-horizon zone (specific A + wildcard + MX/SPF/CAA), made it the primary nameserver in the NetBird home-lab-dns group. Verified all names resolve with dnsmasq/124 stopped; LXC 124 retired.