Docker cleanup cron (host-side)

Purpose:
- Daily prune of unused images/containers/build cache for the runner host.
- Keeps bind-mounted data safe (no named volumes removed).

Schedule:
- 04:00 daily

Cron entry (root):
0 4 * * * root /usr/bin/docker image prune -af --filter "until=24h" && /usr/bin/docker container prune -f && /usr/bin/docker builder prune -af --filter "until=24h"




printf '%s\n' '0 4 * * * root /usr/bin/docker image prune -af --filter "until=24h" && /usr/bin/docker container prune -f && /usr/bin/docker builder prune -af --filter "until=24h"' | sudo tee /etc/cron.d/docker-prune
cat /etc/cron.d/docker-prune