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1. Features
2. Requirements
As stated in the above section you need dar and gpg. The script itself
needs python. So, for a debian based linux distribution you need to
install packages python
, dar
and gnupg
.
3. Details
3.1. Create
Lets assume that you create a backup every day (but it works just the same in case you only do it occasionally).
A full backup (lets call it level one) is created when a series is started. Every n days (can be configured, lets say n=30) a new differential backup against this full backup is created (lets call it level two). In between those level two backups, a number of level three backups are created, which depend on the level one and two and all level three backups since the most current level two backup.
To start a new series (create a new level one backup) tbkp has to be
called with the option --full
.
3.2. Delete
Backups are automatically deleted as explained below.
You’ll always have every backup created since the most recent two level two backups, which means at least latest n days, at most 2*n days.
Level two backups are deleted according to the following scheme in which every hash marks are level two backup and every line marks the creation of a new level two backup. So the one on the right is the most current one.
# 0
# # 1
# # # 2
# # # 3, delete 1
# # # # 4
# # # # 5, delete 3
# # # # 6, delete 2
# # # # 7, delete 5
# # # # # 8
# # # # # 9, delete 7
# # # # # 10, delete 6
# # # # # 11, delete 9
# # # # # 12, delete 4
# # # # # 13, delete 11
# # # # # 14, delete 10
# # # # # 15, delete 13
# # # # # 16, delete 0
# # # # # 17, delete 15
....and so on...
It shows that when number 3 had been created, number 1 was deleted and so on. You can see that backup density is higher for recent backups than for times longer ago. The oldest level 2 backup has an age of at least eight periods, but up to sixteen periods.
In this implemention however, something is deleted a call later than shown above.
3.3. Configuration files
Sample configuration files are included in the download.