# REPORT — agent v0.51.0: local vzdump retention default (`--prune-backups keep-last=3`)

**Date:** 2026-06-30
**Task:** `TASK.md` — local vzdump retention default. The preventive counterpart to the hub's host_disk
(v0.23.0) + storage_fill (v0.25.0) detectors — completing the disk-pressure arc.

## Baseline
| | value |
|---|---|
| felhom-agent | v0.50.0 → **v0.51.0** |
| Commits | `06e0bc9` (agent) · felhom.eu `fdcbc04` (host-install seed) |
| Deployed | felhom-agent 0.51.0 on felhom-pve (prior binary backed up `.bak-0.50.0`); clean restart 46/46 caps |
| VzdumpOptions prune passthrough | **added** — `VzdumpOptions.PruneBackups` → PVE `--prune-backups` on the vzdump POST |

## What changed
The agent's periodic local whole-guest vzdump now prunes its own old archives, so a box can't refill its
own root via its own backups (the felhom-pve incident's root cause — that vzdump carried no retention).
- **`internal/proxmox/mutate.go`:** `VzdumpOptions.PruneBackups` → `--prune-backups` (vmid+storage scoped,
  so PVE prunes only THIS guest's archives on THIS storage).
- **`internal/backup/runner.go`:** `NewBackupRunner` gains `retention`; `localPruneSpec` applies it ONLY
  when the target is a **non-PBS** storage (resolved via `ListStorage`). **Fail-safe:** an unconfirmable
  target type (lookup error / not found) SKIPS pruning rather than risk pruning PBS. Only the periodic
  local-API runner sets retention; restore-test/selftest runners pass "".
- **`internal/config/config.go`:** `backup.local_backup_retention` with `KeepLast()` **clamped ≥1**
  (0/unset/negative → default 3) + `PruneBackupsSpec()` → `keep-last=N`. Wired into the local-API runner.
- **Seeding:** `felhom.eu scripts/felhom-host-install.sh` seeds `local_backup_retention: 3`; the code
  default also protects any box where it's unset (KeepLast → 3) from day 0.
- F2-b stale-vzdump-lock recovery untouched.

## Tests — `go build ./... && go vet ./... && go test ./...` GREEN (Linux build server)
- **flag-present** — a local-target backup carries `--prune-backups keep-last=3`; **companion:** a
  no-retention runner emits NO prune option (dumps would accumulate).
- **PBS never pruned** (scope) — a PBS target gets no prune; **companion:** the same retention on a local
  target IS applied (the gate keys on storage type, not luck). Plus fail-safe-on-unknown-target.
- **clamp** — `LocalBackupRetention` 0/negative/unset → `KeepLast()` ≥1 (default 3); a no-clamp impl
  emitting `keep-last=0` would prune the fresh backup → FAILS the ≥1 assertion.

## Live validation (felhom-pve, real backups — demo dumps expendable)
Triggered the agent's local whole-guest backup of guest 9201 via the local-API `POST /backup` (the exact
path the controller's periodic backup uses; the retention-enabled runner). Pre-state: local held 2 archives
for 9201 (the host_disk task had already pruned the original ~13 to 2), PBS held 8 snapshots, root 24% used.

- Backup #1 → local count **2 → 3** (no deletion yet; 3 ≤ keep-last=3 — the prune flag is exercised but
  retains all 3).
- Each subsequent backup → **prune fired**, local count held at **3** while the retention window slid
  (the oldest rotates out as a new one lands):
  - after #1:        `…10_07_19`, `…11_22_20`, `…19_45_54`
  - after #2:        `…11_22_20`, `…19_45_54`, `…19_51_07`  (`…10_07_19` pruned)
  - after a further: `…19_45_54`, `…19_51_07`, `…19_57_03`  (`…11_22_20` pruned)
  Count never exceeded 3 despite repeated backups (the old no-retention behaviour grew to ~13/18).
- **The real PVE command carried the flag** (from the vzdump task log):
  `vzdump 9201 --mode snapshot --storage local --compress zstd --prune-backups 'keep-last=3' --notes-template 'felhom local-api'`
- **PBS untouched:** felhom-pbs still **8** snapshots for 9201 (the per-run flag never touched the offsite
  repo). Root stayed bounded (24% → 31%, not growing unbounded).

This demonstrates the retention working on real data: repeated local backups stay bounded at keep-last=3
(oldest rotates out) instead of accumulating, and PBS is never pruned.

## Observations
- The disk-pressure arc is now complete: **detectors** (hub host_disk v0.23.0 + storage_fill v0.25.0) +
  **preventive** (this agent-side local-vzdump retention). A box can no longer silently refill its own root
  via its own backups, and if any storage still fills, the operator is paged.
- Remaining disk follow-ons (not blockers): thin-pool *metadata* exhaustion alerting and per-storage-type
  thresholds (both noted in the storage_fill report).

No secrets. Demo backup archives are expendable; PBS offsite retention is a separate lifecycle (untouched).