Problem category
Homelab
Virtual machines and containers.
Docker Container DNS Not Working: Separate IP Path from Name Resolution
Confirm the IP path first, then separate default-bridge and user-defined-bridge resolver behavior when a container reaches external IPs but hostname resolution fails.
Docker Container Has No Internet: Diagnose the Outbound Bridge Path
Separate container state, network mode, addressing, gateway, external IP reachability, and DNS when a running container on rootful Docker Engine bridge networking cannot reach external networks.
Docker Published Port Works Locally but Is Unreachable from the LAN
Compare the working local endpoint with the failing LAN endpoint before investigating publication, application listening context or filtering.
Frigate Says “No Frames Have Been Received”
Use the exact Frigate 0.17.2 Stream Offline message and FFmpeg evidence to separate camera reachability, RTSP authentication/path, input preset, and decode failures without exposing camera credentials.
Immich Upload Fails Through Cloudflare Tunnel While a Trusted Non-Tunnel Path Works
Compare the same Immich upload over a trusted non-Tunnel path and a Cloudflare Tunnel hostname, then classify a Cloudflare-attributed 413, a 524 timeout, a Tunnel origin 502, or an origin-side proxy failure before changing configuration.
Immich Mobile Backup Stalls or Uploads Keep Failing
Verify whether expected originals are actually missing server-side on Immich 3.1.0, then separate album selection, background constraints, proxy path, storage, and dependency failures before touching any data or database.
Jellyfin Playback Failed Due to a Fatal Player Error
Reproduce one failing item on Jellyfin 12.0, correlate the client error with the server and FFmpeg logs at the same timestamp, and isolate whether the failure is at input, transcoding, output storage, or the client path before changing anything.
Nextcloud Shows “Access through untrusted domain”
Confirm the exact Nextcloud untrusted-domain error on 34.0.3, compare the browser hostname with trusted_domains, and make only the narrow trusted-host change supported by the evidence.
Portainer Agent Environment Is Unreachable
Scope the failure to a standard remote Portainer Agent environment, then separate Agent container state, server/Agent version mismatch, port reachability, and TLS evidence on Portainer CE 2.45 LTS.
Proxmox LXC Container Has No Internet: Diagnose Bridge, Gateway and Firewall
Separate container addressing, bridge attachment, gateway reachability, firewall scope, and upstream path when a running Proxmox LXC container cannot reach the external network.
Proxmox VE Host Has No Network After an 8-to-9 Upgrade
From a physical or independent console, compare enumerated links, bridge membership, addresses, and parsed configuration against the known pre-upgrade design after a Proxmox VE 8.4 to 9 upgrade, and stop before any change without recovery access.
Proxmox VM Reaches Its Gateway but Cannot Reach the Internet
Separate guest addressing, resolution, bridge/segment evidence, outbound policy and upstream reachability after confirming the intended gateway responds.
Syncthing Reports “Folder Marker Missing”
Treat .stfolder as a safety guard: prove the configured path, expected filesystem, and expected local data are present before recreating the marker or considering a folder reset in Syncthing 2.1.3.