docker

Docker Image Version Checking

CRITICAL: Always use skopeo to check Docker image versions - never try to parse Docker Hub web pages or use browser scraping.

Why Skopeo

• Reliable: Direct registry API access, not HTML parsing
• Fast: No JavaScript rendering or page loading
• Comprehensive: Works with all OCI-compliant registries
• Accurate: Gets data directly from registry without intermediaries

List Available Tags

# Docker Hub (official images)
skopeo list-tags docker://library/nginx
skopeo list-tags docker://library/postgres

# Docker Hub (user images)
skopeo list-tags docker://username/image
skopeo list-tags docker://rommapp/romm

# Quay.io
skopeo list-tags docker://quay.io/organization/image

# GitHub Container Registry
skopeo list-tags docker://ghcr.io/owner/repo

# Custom registry (like Gitea)
skopeo list-tags docker://git.munchohare.com/jmo/image

Inspect Specific Image/Tag

# Get detailed image information including labels, architecture, layers
skopeo inspect docker://rommapp/romm:4.3.2
skopeo inspect docker://git.munchohare.com/jmo/audioseek-frontend:0.1.11

# Inspect without pulling (faster)
skopeo inspect --no-tags docker://nginx:latest

Registry URL Patterns

Registry	URL Pattern
Docker Hub (official)	docker://library/<image>
Docker Hub (user)	docker://<user>/<image>
Quay.io	docker://quay.io/<org>/<image>
GHCR	docker://ghcr.io/<owner>/<repo>
Custom	docker://<registry>/<path>

Common Use Cases

Find Latest Version

# For semver tags (handles 1.10.0 > 1.9.0 correctly)
skopeo list-tags docker://rommapp/romm | jq -r '.Tags[]' | sort -V | tail -1

Check If Tag Exists

skopeo inspect docker://nginx:1.25 &>/dev/null && echo "exists" || echo "not found"

Compare Image Digests

skopeo inspect docker://nginx:latest | jq -r '.Digest'
skopeo inspect docker://nginx:1.25.3 | jq -r '.Digest'

Get Image Architecture

skopeo inspect docker://nginx:latest | jq -r '.Architecture'