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CalSnap

   

Introduction

calsnap is a minimal shell script that creates backups with Tarsnap. Our design goals:

  • Calendar-based backup schedule
  • Each archive contains all backup targets
  • Just backup, no restore
  • Portable
  • Small code footprint

One daily Tarsnap archive is created per run. By default, 31 daily, 26 weekly, 12 monthly and 4 quarterly backups are kept, and yearly backups are kept indefinitely.

Download

You can use the development version of CalSnap by cloning this repository, or download the latest stable release.

Usage

  1. Take calsnap.conf.sample, customise it for your environment, and save it to /etc/calsnap.conf or /usr/local/etc/calsnap.conf.
  2. Run calsnap daily from cron.

Notes on behavior:

  • calsnap creates archives of the form <hostname>-<period>-yyyy-mm-dd_HH:MM:SS.
    • For weekly archives, the period value is weekly-<year>W<week>, e.g. weekly-2020W53.
    • For quarterly archives, the period value is quarterly-<year>Q<quarter>, e.g. quarterly-2020Q4.
    • The other period values are daily, monthly and yearly.
  • Archives are created using the following logic:
    • Daily archives are created every time calsnap is run.
    • Weekly/monthly/quarterly/yearly archives are copied from the most recent daily archive if they don't exist.
  • Archives are deleted using the following logic by default:
    • If any backups failed, delete nothing.
    • For each backup type, keep only the most recent X backups, and delete any older ones:
      • 31 daily
      • 26 weekly
      • 12 monthly
      • 4 quarterly
      • Unlimited yearly
  • As of 1.2.0, the following limits are recommended instead to increase storage space efficiency while maintaining sufficient coverage:
    • 7 daily
    • 4 weekly
    • 3 monthly
    • 4 quarterly
    • Unlimited yearly

FAQ

  • How do I see the tarsnap output?
    Basically, you don't. calsnap only shows tarsnap output if tarsnap failed. To see what calsnap is doing, you can set verbose=1 in your calsnap.conf. You can get some good tarsnap info, including exactly how much new data this backup consumed, with a prebackupscript. Be sure to set prebackupscript in calsnap.conf to wherever you put this script:
#!/bin/sh

. /etc/calsnap.conf     # Or wherever your calsnap.conf lives
tarsnap --dry-run --quiet --print-stats --humanize-numbers -C / -c $backuptargets 2>&1

History & Comparison

CalSnap is based on ACTS (Another Calendar-based Tarsnap Script) by Alex Jurkiewicz. The ACTS code is robust and continues to be maintained.

The difference between CalSnap and ACTS is the way they handle multiple backup targets: While CalSnap produces one daily archive per run, ACTS produces one daily archive per-run per-target (e.g. MyMachine-daily-...-etc and MyMachine-daily-...-home). See ACTS PR #44 for the detailed rationale of both approaches.

Help

Open a Github issue.

Building

  • Prerequisites
    • make
    • fpm
    • shellcheck (optional)
  • Checking
    • make check
  • Release
    • update VERSION= line in calsnap
    • make