homelab-optimized/docs/admin/IMAGE_UPDATE_GUIDE.md

Docker Image Update Strategy

Last updated: 2026-03-17

Overview

The homelab uses a multi-layered approach to keeping Docker images up to date, combining automated detection, GitOps deployment, and manual controls.

Renovate (weekly scan) ──► Creates PR with version bumps
                                    │
                              Merge PR to main
                                    │
portainer-deploy.yml (CI) ──► Redeploys changed stacks (pullImage=true)
                                    │
                              Images pulled & containers recreated
                                    │
DIUN (weekly scan) ──────► Notifies via ntfy if images still outdated
                                    │
Watchtower (on-demand) ──► Manual trigger for emergency updates

Update Mechanisms

1. Renovate Bot (Recommended — GitOps)

Renovate scans all compose files weekly and creates PRs to bump image tags.

Setting	Value
Schedule	Mondays 06:00 UTC
Workflow	.gitea/workflows/renovate.yml
Config	renovate.json
Automerge	No (requires manual review)
Minimum age	3 days (avoids broken releases)
Scope	All docker-compose files in hosts/

How it works:

1. Renovate detects new image versions in compose files
2. Creates a PR on Gitea (e.g., "Update linuxserver/sonarr to v4.1.2")
3. You review and merge the PR
4. portainer-deploy.yml CI triggers and redeploys the stack with pullImage: true
5. Portainer pulls the new image and recreates the container

Manual trigger:

# Run Renovate on-demand from Gitea UI:
# Actions → renovate → Run workflow

2. Portainer GitOps Auto-Deploy (CI/CD)

When compose files are pushed to main, the CI workflow auto-redeploys affected stacks.

Setting	Value
Workflow	.gitea/workflows/portainer-deploy.yml
Trigger	Push to main touching hosts/** or common/**
Pull images	Yes (pullImage: true in redeploy request)
Endpoints	Atlantis, Calypso, NUC, Homelab VM, RPi 5

All stacks across all endpoints are GitOps-linked (as of 2026-03-17). Every stack has a GitConfig pointing to the repo, so any compose file change triggers an automatic redeploy.

To update a specific service manually via GitOps:

# Edit the compose file to bump the image tag
vim hosts/synology/atlantis/sonarr.yaml
# Change: image: linuxserver/sonarr:latest
# To:     image: linuxserver/sonarr:4.1.2

# Commit and push
git add hosts/synology/atlantis/sonarr.yaml
git commit -m "feat: update sonarr to 4.1.2"
git push
# CI auto-deploys within ~30 seconds

3. DIUN — Docker Image Update Notifier (Detection)

DIUN monitors all running containers and sends ntfy notifications when upstream images have new digests.

Setting	Value
Host	Atlantis
Schedule	Mondays 09:00 UTC (3 hours after Renovate)
Compose	hosts/synology/atlantis/diun.yaml
Notifications	ntfy topic diun (https://ntfy.vish.gg/diun)

DIUN is detection-only — it tells you what's outdated but doesn't update anything. If Renovate missed something (e.g., a :latest tag with a new digest), DIUN will catch it.

4. Watchtower (On-Demand Manual Updates)

Watchtower runs on 3 endpoints with automatic updates disabled. It's configured for manual HTTP API triggers only.

Setting	Value
Hosts	Atlantis, Calypso, Homelab VM
Schedule	Disabled (manual only)
Compose	common/watchtower-full.yaml
API port	8083 (configurable via WATCHTOWER_PORT)
Notifications	ntfy via shoutrrr

Trigger a manual update on a specific host:

# Atlantis
curl -X POST http://192.168.0.200:8083/v1/update \
  -H "Authorization: Bearer watchtower-metrics-token"

# Calypso
curl -X POST http://192.168.0.250:8083/v1/update \
  -H "Authorization: Bearer watchtower-metrics-token"

# Homelab VM
curl -X POST http://localhost:8083/v1/update \
  -H "Authorization: Bearer watchtower-metrics-token"

This pulls the latest image for every container on that host and recreates any that have newer images. Use sparingly — it updates everything at once.

Exclude a container from Watchtower:

labels:
  - "com.centurylinklabs.watchtower.enable=false"

5. Portainer UI (Manual Per-Stack)

For individual stack updates via the Portainer web UI:

1. Go to https://192.168.0.200:9443
2. Navigate to Stacks → select the stack
3. Click Pull and redeploy (pulls latest images)
4. Or click Update the stack → check "Pull latest image"

Recommended Workflow

Weekly Routine (Automated)

Monday 06:00 UTC  →  Renovate creates PRs for version bumps
Monday 09:00 UTC  →  DIUN sends digest change notifications

1. Check ntfy for DIUN notifications and Gitea for Renovate PRs
2. Review and merge Renovate PRs (CI auto-deploys)
3. For :latest tag updates (no version to bump), trigger Watchtower manually

Updating a Single Service

# Option A: Via Portainer UI
# Stacks → stack-name → Pull and redeploy

# Option B: Via git (recommended for traceability)
# Edit compose, commit, push → CI deploys

# Option C: Via Watchtower API (updates all containers on that host)
curl -X POST http://<host>:8083/v1/update \
  -H "Authorization: Bearer watchtower-metrics-token"

# Option D: Via Ansible (for system packages, not Docker)
ansible-playbook -i ansible/inventory.yml \
  ansible/automation/playbooks/update_system.yml --limit <host>

Updating All Services on a Host

# Trigger Watchtower on the host
curl -X POST http://<host-ip>:8083/v1/update \
  -H "Authorization: Bearer watchtower-metrics-token"

# Or redeploy all stacks via Portainer API
# (the portainer-deploy CI does this automatically on git push)

Image Tagging Strategy

Strategy	Used By	Pros	Cons
:latest	Most services	Always newest, simple	Can break, no rollback, Renovate can't bump
:version (e.g., :4.1.2)	Critical services	Deterministic, Renovate can bump	Requires manual/Renovate updates
:major (e.g., :4)	Some LinuxServer images	Auto-updates within major	May get breaking minor changes

Recommendation: Use specific version tags for critical services (Plex, Sonarr, Radarr, Authentik, Gitea, PostgreSQL). Use :latest for non-critical/replaceable services (IT-Tools, theme-park, iperf3).

Services NOT Auto-Updated

These services should be updated manually with care:

Service	Reason
Gitea	CI runs on Gitea — auto-deploying can break CI itself
Authentik	SSO provider — broken update locks out all services
PostgreSQL	Database — major version upgrades require migration
Portainer	Container orchestrator — update via DSM or manual Docker commands

Monitoring Update Status

# Check which images are outdated (via DIUN ntfy topic)
# Subscribe to: https://ntfy.vish.gg/diun

# Check Watchtower metrics
curl http://192.168.0.200:8083/v1/metrics \
  -H "Authorization: Bearer watchtower-metrics-token"

# Check running image digests vs remote
docker images --digests | grep <image-name>

Related Documentation

• Ansible Playbook Guide — System package updates
• Portainer API Guide — Stack management API
• GitOps Guide — CI/CD pipeline details