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Adds title, description, type, domain, and tags frontmatter to every doc for improved KB semantic search. The description field is prepended to every search chunk, and domain/type/tags enable filtered queries. Type values: context, guide, runbook, reference, troubleshooting Domain values match directory structure (networking, docker, etc.) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
120 lines
3.4 KiB
Markdown
120 lines
3.4 KiB
Markdown
---
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title: "Pi-hole Disk Optimization"
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description: "Resolved critical disk space issue on primary Pi-hole by reducing query log retention to 7 days, pruning Docker resources, and removing old gravity backups."
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type: runbook
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domain: networking
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tags: [pihole, disk-space, docker, optimization, maintenance]
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---
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# Pi-hole Disk Optimization - 2026-02-06
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## Problem
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Primary Pi-hole (npm-pihole at 10.10.0.16) had critical disk space issues:
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- **Root filesystem**: 91% full (27GB used of 31GB)
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- **Pi-hole data**: 3.6GB total
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- `pihole-FTL.db`: 2.8GB (query log database)
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- `gravity.db`: 460MB (blocklist database)
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- `gravity.db.v5.backup`: 114MB (old v5 backup)
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- **Query retention**: 91 days (default)
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- **Total queries stored**: 26.4 million
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## Actions Taken
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### 1. Removed Old Backup Database
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```bash
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rm /home/cal/container-data/pihole/etc-pihole/gravity.db.v5.backup
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```
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**Space freed**: 114MB
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### 2. Cleaned Up Docker Resources
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```bash
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docker system prune -af --volumes
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```
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**Space freed**: 4.3GB
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- Removed unused images (old Pi-hole versions, Jellyfin, Foundry, etc.)
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- Removed stopped containers
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- Removed unused networks
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### 3. Reduced Query Log Retention
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```bash
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echo "database.maxDBdays=7.0" >> /etc/pihole/pihole-FTL.conf
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docker compose restart
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```
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**Configuration**: Changed from 91 days to 7 days
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**Future savings**: Database will automatically maintain ~7 days of logs instead of 91
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## Results
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| Metric | Before | After | Improvement |
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|--------|--------|-------|-------------|
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| Disk Usage | 91% (27GB/31GB) | 73% (22GB/31GB) | -18% |
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| Free Space | 2.8GB | 8.2GB | +5.4GB |
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| Total Freed | - | 4.3GB | - |
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## Ongoing Maintenance
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### Automatic Cleanup
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Pi-hole will now automatically:
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- Delete queries older than 7 days
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- Maintain FTL database size around ~300-500MB (instead of 2.8GB)
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- Keep the most recent week of query logs for troubleshooting
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### Manual Cleanup (if needed)
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```bash
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# Flush Pi-hole logs
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docker exec pihole pihole -f
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# Check disk usage
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df -h /
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du -sh /home/cal/container-data/pihole/etc-pihole/*
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# Clean unused Docker resources
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docker system prune -af --volumes
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# Check query count
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docker exec pihole pihole-FTL sqlite3 /etc/pihole/pihole-FTL.db 'SELECT COUNT(*) FROM queries;'
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```
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### Monitoring Recommendations
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**Set up disk space alerts** when usage exceeds 85%:
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```bash
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# Add to cron (daily check)
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0 8 * * * df -h / | awk '$5+0 > 85 {print "Warning: Disk usage at " $5 " on npm-pihole"}' | mail -s "Disk Alert" admin@example.com
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```
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**Check Pi-hole database size monthly**:
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```bash
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du -h /home/cal/container-data/pihole/etc-pihole/pihole-FTL.db
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```
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## Configuration File
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`/etc/pihole/pihole-FTL.conf`:
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```conf
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database.maxDBdays=7.0 # Keep queries for 7 days only
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```
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## Prevention Tips
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1. **Regular Docker cleanup**: Run `docker system prune` monthly
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2. **Monitor disk usage**: Check `df -h` weekly
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3. **Review query retention**: 7 days is sufficient for most troubleshooting
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4. **Consider disabling query logging** if not needed:
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```bash
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pihole logging off
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```
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5. **Archive old logs** before major upgrades (like v5→v6)
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## Space Budget Estimates
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With 7-day retention:
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- **Pi-hole FTL database**: ~300-500MB (vs 2.8GB before)
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- **Gravity database**: ~460MB (36 blocklists)
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- **Docker images**: ~2-3GB (active containers only)
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- **System overhead**: ~20GB
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- **Recommended free space**: 5GB+ for headroom
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**Current allocation is healthy** at 73% with 8.2GB free.
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