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Machine: acg-guru-5070
Timestamp: 2026-03-19 19:25:24

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/forum-posts/cachyos-tailscale-fix.md

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+# Fix: Tailscale Health Warnings on CachyOS (Arch) with KDE Plasma
+
+## Environment
+- OS: CachyOS (Arch-based), kernel 6.19.7-1-cachyos
+- DE: KDE Plasma 6 (Wayland)
+- Tailscale: 1.94.2
+
+## Problem
+
+`tailscale status` showed two health warnings:
+
+```
+# Health check:
+#     - systemd-resolved and NetworkManager are wired together incorrectly; MagicDNS will probably not work.
+#     - Some peers are advertising routes but --accept-routes is false
+```
+
+## Diagnosis
+
+### Issue 1: Accept Routes
+Peers (pfSense, NAS) were advertising subnet routes but the machine wasn't accepting them:
+```bash
+tailscale status --json | python3 -c "
+import json,sys
+d=json.load(sys.stdin)
+for k,v in d.get('Peer',{}).items():
+    routes = v.get('PrimaryRoutes', [])
+    if routes:
+        print(f\"{v['HostName']}: {routes}\")
+"
+# Output: pfSense: ['172.16.0.0/22'], D2TESTNAS: ['192.168.0.0/24']
+```
+
+### Issue 2: DNS Wiring
+```bash
+resolvectl status
+# resolv.conf mode: foreign   <-- WRONG, should be "stub"
+
+ls -la /etc/resolv.conf
+# -rw-r--r-- 1 root root 86 ...   <-- regular file, NOT a symlink
+
+cat /etc/NetworkManager/NetworkManager.conf
+# Empty - no dns= directive
+```
+
+NetworkManager was generating `/etc/resolv.conf` directly instead of going through systemd-resolved. Tailscale needs systemd-resolved to handle MagicDNS (.ts.net) queries.
+
+## Fix
+
+### Fix 1: Accept Routes
+```bash
+sudo tailscale set --accept-routes
+```
+
+### Fix 2: Wire NetworkManager to systemd-resolved
+
+Step 1 - Tell NetworkManager to use systemd-resolved as DNS backend:
+```bash
+sudo tee /etc/NetworkManager/conf.d/dns.conf > /dev/null << 'EOF'
+[main]
+dns=systemd-resolved
+EOF
+```
+
+Step 2 - Fix the resolv.conf symlink:
+```bash
+sudo ln -sf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
+```
+
+Step 3 - Restart services:
+```bash
+sudo systemctl restart NetworkManager
+sudo systemctl restart systemd-resolved
+sudo systemctl restart tailscaled
+```
+
+## Verification
+
+```bash
+resolvectl status
+# resolv.conf mode: stub   <-- CORRECT
+
+tailscale status
+# No health warnings
+
+ping d2testnas
+# PING d2testnas.tailea2889.ts.net (100.85.152.90) - MagicDNS working
+```
+
+## Why This Happens
+
+CachyOS (and many Arch installs) ship with both NetworkManager and systemd-resolved active, but NetworkManager isn't configured to delegate DNS to systemd-resolved. It writes `/etc/resolv.conf` directly, bypassing the resolved stub. Tailscale configures its MagicDNS via systemd-resolved's D-Bus API, so if resolved isn't actually handling queries, `.ts.net` names won't resolve.