Bits of .NET

🐳 No Space Left ≠ Delete Your Volumes

Docker throwing no space left on device makes it tempting to start deleting things fast — but the actual culprit is almost always accumulated build cache, dangling images, and stopped containers, none of which hold data you need.

🔍 Find What’s Actually Eating Space First

docker system df -v
# Shows a breakdown: Images, Containers, Local Volumes, Build Cache
# - usually "Build Cache" and dangling "<none>" images are the
# biggest, most disposable offenders, often for many GB.

✅ Safe Cleanup, Broadest to Narrowest

• Start with the safest command and check if it freed enough space before reaching for anything broader.
• None of the commands below touch named volumes by default — that’s the deliberate safety boundary.

🧹 Cleanup Commands, Safest First

# Removes stopped containers, dangling images, unused networks,
# and build cache - does NOT touch volumes or running containers
docker system prune

# Also removes images not currently used by ANY container
# (not just dangling ones) - more aggressive but still volume-safe
docker system prune -a

# Only if you're SURE: also removes unused volumes.
# This DOES delete data if a volume isn't attached to a container
# right now - check "docker volume ls" and inspect first.
docker system prune -a --volumes

⚠️ Before You Add –volumes

• Run ‘docker volume ls’ and cross-check each one against ‘docker ps -a’ — a volume for a container you stopped last week but plan to restart is NOT safe to delete.
• Named volumes for databases (Postgres, MySQL, etc.) hold your actual data — deleting them is equivalent to dropping the database.