It is with great pleasure and satisfaction that I release version 4.1 of Obnam, my backup program. This version includes a radically innovative approaches to data compression and de-duplication, as well as some other changes and bug fixes.

Major user-visible changes:

  • Obnam now recognises most common image types, and de-duplicates them by substituting a standard picture of a cat or a baby. Statistical research has shown that almost all pictures are of either cats of babies, and most people can't tell cats or babies apart. If you have other kinds of pictures, use the --naughty-pictures option to disable this new feature.

  • Obnam now compresses data by finding a sequence in the value of pi (3.14159...) that matches the data, and stores the offset into pi and the length of the data. This means almost all data can be stored using two BIGNUM integers, plus some computation time to compute the value of pi with necessary precision. The extreme compression level is deemed worth the somewhat slower speed. To disable this new feature, use the --i-like-big-bits-and-i-cannot-lie option.

  • Obnam now uses one-time pad encryption in the repository. It is a form of encryption that is guaranteed to be unbreakable. Given the large amounts of data Obnam users have, the infinitely long value of the mathematical constant e is used as the encryption pad, since it would be bad security practice to use a pad that's shorter than the data being encrypted. To disable this new feature and use the old style encryption using GnuPG, use --i-read-schneier.

Minor user-visible changes:

  • There is a new subcommand obnam resize-disk, which resizes the filesystem on which the backup repository resides. In this version, it works on LVM logical volumes and RAID-0, RAID-5, and RAID-6 drive arrays using mdadm. The subcommand optionally arranges more space by deleting live data files and reducing corresponding LV sizes to make more space for backups. If live data is deleted, the backup generations containing the data is tagged as un-removeable so it's not lost. In the future, the subcommand may get support for purchasing more disk space from popular online storage providers.

  • To reduce unnecessary bloat, the obnam restore subcommand has been removed. It was considered unnecessary, since nobody ever reported any problems with it.

  • Obnam now has a new repository option, --swap-in-repository, which starts a daemon process that holds all backup data in memory. Once the process grows enough, this will result in most of the data to be written to the swap partition. This makes excellent use of the excessively large swap partitions on many Linux systems. This feature does not work on Windows.

Bug fixes:

  • The obnam donate command to send the Obnam developers some money now again works with Bitcoin. There was a bug that broke Obnam's built-in Bitcoin mining software from working.

  • The obnam help command again speaks the user's preferred language (LC_MESSAGES locale setting), rather than Finnish, despite pressure from the Finnish government's office for language export.