torbenandClaude Opus 5.5
fe1de63e0f
Files changed: - CHANGES.md - INSTALL.md - README.md - VERSION - docs/reference/commands/types-instructions-and-docs.md - docs/tutorials/README.md - docs/tutorials/first-source-to-first-answer.md - docs/tutorials/sample-source.md - instructions/dev/doc-pull-through.md - tools/CONTRACT.md - tools/chemenu/commands/docs_verify.py - tools/chemenu/install_doc.py - tools/chemenu/tests/test_install_doc.py Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2
49 lines
2.1 KiB
Markdown
49 lines
2.1 KiB
Markdown
# Home lab backups - how they work now
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Notes written after reworking the backups in September 2026. This file is the sample source for
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the tutorial "From your first source to your first answer"; the machine and its setup are made
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up for it.
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## The machine
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**Atlas** is the small file server in the hall cupboard: a fanless mini PC with two 4 TB disks
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in a mirror, running Debian 13. It holds the family photo archive, scanned documents and the
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configuration of every other machine in the house. Everything else on the network is replaceable;
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what is on Atlas is not.
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## The tool
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Backups are made with **restic**, an open-source backup program. restic splits files into chunks,
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stores each chunk only once and encrypts everything before it leaves the machine, so the backup
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target never sees a file name or a byte of content in the clear. A restic *repository* is the
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storage location it writes to; a *snapshot* is one backup run.
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restic was chosen over plain `rsync` for two reasons: deduplication keeps the daily runs small,
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and encryption makes it safe to put a copy on storage someone else operates.
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## How it is set up
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Atlas runs restic every night at 02:30 from a systemd timer. Each run writes one snapshot to two
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repositories:
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- a USB disk that stays plugged into Atlas, for fast restores;
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- a rented storage box at a hosting provider, reached over SFTP, as the copy outside the house.
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Snapshots are thinned out by `restic forget` after each run: the last 7 daily, 5 weekly and
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12 monthly snapshots are kept.
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## Why two targets
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The setup follows the **3-2-1 backup rule**: keep three copies of the data, on two different
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kinds of storage, with one copy off site. Here the three copies are the mirror on Atlas itself,
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the USB disk, and the storage box. A fire or a burglary takes the first two; the storage box is
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what is left.
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The mirror alone does not count as a backup. It protects against a dead disk, but a deleted or
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encrypted file is deleted or encrypted on both disks at once.
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## What is still open
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The restore has been tried once, for a single folder, from the USB disk. It worked and took
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under a minute. A full restore from the storage box has not been tried.
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