Julien LutranandClaude Fable 5
b5aef914f5
Decided 2026-08-28: instances are protected by replication (sdb now, nuc after FTTH, ks2 push in between), their data/DBs/configs by restic-data — a third copy of instance filesystems in S3 was not worth the moving parts. backup-strategy.md now explains the replication-vs-backup split and the rebuild path when no replica survives; restic-backup.md §6 is marked SHELVED (script and empty repo kept). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
123 lines
7.0 KiB
Markdown
123 lines
7.0 KiB
Markdown
# ks4 backup strategy (2026-08)
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Audience: anyone with root on ks4 who needs to know **what is protected,
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where, by which tool, and how to check it**. Details live in the linked
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docs; this page is the map.
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## Two tools, no more
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| tool | job | why this one |
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| **`incus copy --refresh`** | replicate whole instances (ready-to-start copies) | ZFS-incremental, native to the platform, restores are `incus start` |
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| **restic** | off-site backups to S3 (files, database dumps, instance trees) | dedup + encryption, local metadata cache → a night costs only the churn ([restic-backup.md](ks4/restic-backup.md)) |
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plakar was evaluated first and replaced (its nightly cost scaled with
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tree size — [PlakarKorp/plakar#2338](https://github.com/PlakarKorp/plakar/issues/2338));
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the old backup server **ks2 is being retired** (decommission by
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Sep 30, 2026 — [ks2/plan.md](ks2/plan.md)): it still holds an ageing
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copy of the instances until the nuc leg below takes over.
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**Status 2026-08-28**: the local replica leg and the S3 data leg are
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live. The **nuc pull leg is waiting for FTTH** (expected before end of
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September); until it lands, the ks2 push is re-enabled as an interim
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off-site copy of the instances. Backing up instance *images* to S3 was
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designed and shelved — S3 holds the data, the databases and the incus
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configuration, which is what a rebuild needs.
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## The map
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```
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ks4 (OVH) off-site
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┌────────────────────────────────────────────┐
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│ live instances pool `data` (sda) │
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│ nextcloud, seafile, mail, git, ... │
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│ │ │
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│ │ 01:00 incus copy --refresh │ nuc (home LAN, via WireGuard)
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│ ▼ │ ┌───────────────────────────┐
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│ replicas (stopped) pool `backup` (sdb) │────▶│ 05:00 incus copy (pull) │
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│ project `backup` ready to start │ │ pool `ks4backup` (USB) │
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│ │ └───────────────────────────┘
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│ ──────────────────────────────────────── │
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│ │ OVH Object Storage (S3, sbg)
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│ 05:00 restic-backup.sh │ ┌───────────────────────────┐
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│ • DB dumps (MariaDB/PostgreSQL, auto) │────▶│ bucket restic-data │
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│ • incus config + global DB dump │ │ everything needed to │
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│ • data trees (restic-paths) │ │ rebuild: dumps + data │
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│ │ └───────────────────────────┘
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│ Sun 14:00 restic-maintenance.sh │
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│ • prune + check (rotating full verify) │
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└────────────────────────────────────────────┘
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```
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Two different kinds of protection, on purpose:
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- **instances** (the running systems) are protected by *replication* —
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a ready-to-start copy on ks4's second disk and, after FTTH, on nuc.
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Restoring one is `incus copy` + `incus start`.
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- **the data inside them** (files, databases, incus configuration) is
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protected by *backup* — encrypted, deduplicated, versioned on S3,
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independent of ks4 and of the disks. Restoring means recreating the
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container (its config is in the S3 dumps, its install steps are in
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this repo) and pouring the data back.
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Backing up whole instance images to S3 as well was designed
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([ks4/restic-backup.md](ks4/restic-backup.md) §6) and shelved: it
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duplicates data already covered, and the replication legs already give
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instances two homes.
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## Schedule (root crontab on ks4)
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| when | what | log |
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| 01:00 daily | `incus-copy.sh -p backup -s backup` — refresh all replicas onto sdb | `/var/log/incus-copy.log` |
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| 02:00 daily | `incus-copy.sh -d ks2 -m push` — interim off-site replicas, until the nuc leg replaces it | `/var/log/incus-copy.log` |
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| 03:00 daily | instance snapshots (incus profile, 7-day expiry) — what keeps the refreshes incremental | `incus info <inst>` |
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| 05:00 daily | `restic-backup.sh` — dumps + data trees → S3 | `/var/log/restic-backup.log` |
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| 05:00 daily (nuc) | nuc pulls all replicas over WireGuard | nuc: `/var/log/incus-copy-ks4.log` |
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| Sun 14:00 | `restic-maintenance.sh` — prune (capped), structure check, 1/52 data verification | `/var/log/restic-maintenance.log` |
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| 1st of month 06:00 / quarterly 15th | seafile GC dry-run report / real GC ([ks4/seafile-gc.md](ks4/seafile-gc.md)) | `/var/log/seafile-gc.log` |
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Retention on S3: 14 daily, 8 weekly, 6 monthly snapshots.
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## "Did last night work?" — the 30-second check
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```sh
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grep -aE "done \(rc=|FAILED" /var/log/incus-copy.log | tail -2
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grep -aE "snapshot .* saved|done \(rc=|failed" /var/log/restic-backup.log | tail -3
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```
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`rc=0` everywhere = fine. Any `failed`/`FAILED` line names the culprit
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(instance, database or path). All scripts exit non-zero on any error,
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never silently.
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## Restoring
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- **A whole instance, fast (same box)**: `incus copy backup:<inst>`
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style — copy the replica from project `backup` back into `default`
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([ks4/incus-copy.md](ks4/incus-copy.md)); from nuc the same via the
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remote.
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- **A file or directory** (any date within retention):
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`restic -r s3:s3.sbg.io.cloud.ovh.net/restic-data restore <snapshot> --target /backup/restore-x --include <path>`
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(never restore into `/tmp` — it is RAM). Env: `. /root/.restic-env`.
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- **A database**: restore the `.sql` dump from `restic-data`
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(`/backup/dumps/mariadb/<inst>/<db>.sql`, `grants.sql` for users), load
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it with `incus exec <inst> -- mariadb < dump.sql`.
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- **An instance when no replica survives** (worst case: ks4 and the
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replica sites are gone): recreate the container from its page in
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[ks4/](ks4/) (the doc *is* the install script), restore its data
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trees and database dumps from `restic-data`, and use the incus
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configuration captured nightly in the dump tree
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(`/backup/dumps/incus/incus-global-db.sql`) to check devices,
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profiles and addresses.
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Secrets you need for any of this: `/root/.restic-passphrase` and the S3
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keys in `/root/.restic-env` — **both are in the password manager**;
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without the passphrase the S3 buckets are unreadable.
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## Adding something to the backups
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New instances are picked up automatically by the replica and
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instance legs (all instances, opt-out only). Databases are
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auto-discovered. Only **data trees** need one line in
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[`restic-paths`](https://git.lutran.fr/julien/scripts/src/branch/main/restic-paths) — see [new-container.md](new-container.md).
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