Tarsnapper

A wrapper around tarsnap which does two things:

• Lets you define "backup jobs" (tarsnap invocations) in a config file, though on it's own this has little advantage over just using a a shell script.
• The ability to expire old backups using a Grandfather-father-son backup scheme. This feature can be used in conjunction with tarsnapper backup jobs, or standalone, to be applied to any existing set of tarsnap backup archives, regardless of how they have been created.

Installation

Using easy_install:

$ apt-get install python-setuptools
$ easy_install tarsnapper

Basic usage

Create backups based on the jobs defined in the configuration file (see below for information about the config file format):

$ tarsnapper -c myconfigfile make

Specify a job on the command line: In this case, we use the "expire" command, so no backups will be created, but only old backups deleted:

$ tarsnapper --target "foobar-\$date" --deltas 1d 7d 30d - expire

The --target argument selects which set of backups to apply the expire operation to. tarsnapper will try to match the archives it finds into the given delta range, and will delete those which seem unnecessary.

Note the single "-" that needs to be given between the --deltas argument and the command.

The expire command supports a --dry-run argument that will allow you to see what would be deleted:

$ tarsnapper --target "foobar-$date" --deltas 1d 7d 30d - expire --dry-run

If you need to pass arguments through to tarsnap, you can do this as well:

$ tarsnapper -o configfile tarsnap.conf -o v -c tarsnapper.conf make

This will use tarsnap.conf as the tarsnap configuration file, tarnspapper.conf as the tarsnapper configuration file, and will also put tarsnap into verbose mode via the -v flag.

The config file

Example:

# Global values, valid for all jobs unless overridden:
deltas: 1d 7d 30d
target: /localmachine/$name-$date

jobs:
  images:
    source: /var/lib/mysql
    exclude: /var/lib/mysql/temp
    exec_before: service stop mysql
    exec_after: service start mysql
    # Aliases can be used when renaming a job to match old archives.
    alias: img

  some-other-job:
    sources:
      - /var/dir/1
      - /etc/google
    excludes:
      - /etc/google/cache
    target: /custom-target-$date.zip
    deltas: 1h 6h 1d 7d 24d 180d

For the images job, the global target will be used, with the name placeholder replaced by the backup job name, in this case images.

How expiring backups works

The approach chosen tries to achieve the following:

• Do not require backup names to include information on which generation a backup belongs to, like for example tarsnap-generations does. That is, you can create your backups anyway you wish, and simply use this utility to delete old backups.
• Do not use any fixed generations (weekly, monthly etc), but freeform timespans.
• Similarily, do not make any assumptions about when or if backup jobs have actually run or will run, but try to match the given deltas as closely as possible.

The generations are defined by a list of deltas. 60 means a minute, 12h is half a day, 7d is a week. The number of backups in each generation is implied by it's and the parent generation's delta.

For example, given the deltas 1h 1d 7d, the first generation will consist of 24 backups each one hour older than the previous (or the closest approximation possible given the available backups), the second generation of 7 backups each one day older than the previous, and backups older than 7 days will be discarded for good.

The most recent backup is always kept.