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diff --git a/DOCUMENTATION b/DOCUMENTATION deleted file mode 100644 index 9d346b4..0000000 --- a/DOCUMENTATION +++ /dev/null @@ -1,63 +0,0 @@ -SquashFu - an alternative backup solution - Inspired by http://forums.gentoo.org/viewtopic-p-4732709.html - -Requirements: aufs, aufs2-util, squashfs-tools, rsync, bc - -Goal: To create a backup solution which provides incremental backups and compression, - and which also provides an easy way to roll back. - -Design: - A directory structure is created as follows (with some terminology included): - backup_root/ - |- seed.sfs <-- squash, or seed - |- .bin.list <-- bin inventory list (or binventory) - |- ro/ <-- squash mount point - |- rw/ <-- union mount point - |- .bins/ <-- incrementals - |-1/ - | ..... - | ..... - | ..... - | ..... - | ..... - |-n/ - - 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 - unmounted. - - 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 - point. - -WARNING: - 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: - http://en.wikipedia.org/wiki/Aufs - http://en.wikipedia.org/wiki/UnionFS - http://aufs.sourceforge.net/ - http://en.wikipedia.org/wiki/SquashFS - http://en.wikipedia.org/wiki/Rsync - |