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A backup program employing the use of SquashFS, Aufs and Rsync
Shell Perl
Tag: 0.8-beta

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SquashFu - a combination of fun, squashfs, joy, happiness, aufs and rsync
REQUIREMENTS: aufs, aufs2-util, squashfs-tools, rsync


Mini FAQ:

What currently works?
 - Regular incrementals. Execute with sudo and the -B option
 - Automatic merging incremenetals down to MIN_BINS once MAX_BINS has been exceeded
 - Rolling back. Execute with sudo, the -R option, and a number of backups to roll back
 - Reporting, executed with -Q, shows approx. disk usage and bin information

What's not yet included?
 - Options (don't expect a lot of them)
 - A lot of error catching. No telling what will happen if you SIGINT in the middle of
   a resquash, for example. Rsync takes care of itself, however.

What not to expect?
 - Elephants
 - Salvation

If you don't care about your cat...

Goal: To create a backup solution which provides incremental backups and compression,
      and which also provides an easy way to roll back.

  A directory structure is created as follows (with some terminology included):
       |- seed.sfs  <-- squash, or seed
       |- .bin.list <-- bin inventory list (or binventory)
       |- ro/       <-- squash mount point
       |- rw/       <-- union mount point
       |- .bins/    <-- incrementals
           | .....
           | .....
           | .....
           | .....
           | .....

  seed.sfs is created from an initial backup and compressed using SquashFS, which is
  simply a filesystem which focuses on compression, but is read only. It's mounted,
  using a loopback device, on ro/. Using aufs2, a union mount is formed by ro/ and each 
  of the numbered bins, each corresponding to an incremental backup.

  At the time of the backup, the next available bin is created and logged to an inventory
  sheet with a timestamp. A union is created with all the available bins, mounted in
  reverse chronological order on top of the seed (newest to oldest) on rw/. At this point,
  the union represents the state of your files at the end of the last backup. The newest
  branch is marked as read/write, and rsync is called. Because this top branch is the
  only writable location in the union, the files rsync generates with the -u (update)
  flag are placed into this branch. The backup finishes, and the union and seed are

  At this point, Squashfu ensures compliance with the user's settings of MAX_BINS. If
  the current number of used bins exceeds this value, a new seed is generated. The 
  number of old incrementals merged into the new seed is determined by the difference
  between MAX_BINS and MIN_BINS in the config file. In this way, you always have
  MIN_BINS available to roll back to, but you're not forced to recompress your seed
  at every backup -- an operation that may take a long time depending on how big
  your backup source is.

  If and when you want to roll back, execute Squashfu with the -R action, and supply
  the number of bins you want to roll back. The bins are ordered chronologically,
  and the oldest "number_of_bins - bins_to_rollback" are mounted on the union mount

  You should not, under any circumstances, add or remove files contained in the bins, 
  nor should you alter your binventory's time stamps. Doing so can result in non-recoverable
  damage to the integrity of the backups.

Further reading:

-Copy squashfu.conf as /etc/squashfu.conf
-Make a backup directory somewhere where you want your files
-READ OVER /etc/squashfu.conf and set it the way you want
-Run manually with 'squashfu -B'
-If everything goes well, make a cron job to run this bad boy at the time you want
-Hang onto ya nuts. As this is still an alpha, I take no responsibility for
 loss of data, and I likely don't care much about bug reports.

1/11/2010 (Kernel:
    Issue: Aufs takes a long time to unmount.
    Fix:   If using Ext4, mount with the 'nobarrier' option. No resolution known
           at this time for other FS's.

In no particular order....

- Create dispatchers for actions (mostly done)
- Create options parser (and determine options)
- Limit access by checking for sudo
- Fix output funcs for non-color scenario

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