pachy

pachy is a simple Python script to create incremental backups using rsync and xdelta3:

• By using rsync backups require little bandwidth;
• By using xdelta3, incremental backups use little space;
• The codebase is very small; thus easy to adapt to your own needs.

Getting started

Installing pachy

You will need Python's setuptools; xz-utils rsync and xdelta3. On Debian Linux, execute:

$ apt-get install python-setuptools rsync xdelta3 xz-utils

Then, to install pachy:

$ easy_install pachy

Example: local backups

In this example we will backup our ~/Document folder that contains:

.
├── dir1
│   ├── document2
│   └── document3
└── example1

First backup

To create a backup of ~/Documents to /mnt/disk/Backup, execute:

$ pachy ~/Documents /mnt/disk/Backup
INFO:root:0. Checking set-up
INFO:root:1. Running rsync
sending incremental file list
./
example1
dir1/
dir1/document2
dir1/document3

sent 237 bytes  received 76 bytes  626.00 bytes/sec
total size is 0  speedup is 0.00
INFO:root:2. Checking for changes
INFO:root:3. Creating archive
INFO:root:4. Cleaning up

Incremental backups

After some work we changed the file example1 and deleted document2. To create an incremental backup, just run the same command a second time. Only changes will be copied.

$ pachy ~/Documents /mnt/disk/Backup
INFO:root:0. Checking set-up
INFO:root:1. Running rsync
sending incremental file list
./
example1
dir1/
deleting dir1/document2

sent 161 bytes  received 38 bytes  398.00 bytes/sec
total size is 9  speedup is 0.05
INFO:root:2. Checking for changes
INFO:root:3. Creating archive
INFO:root:4. Cleaning up

Backup format

If you look at /mnt/disk/Backup you will find it contains:

.
├── deltas
│   └── 2012-02-05@14h13.02.tar.xz
└── mirror
    ├── dir1
    │   └── document3
    └── example1

The mirror subdirectory is an exact copy of the ~/Documents folder. Under deltas there is for each incremental backup a .tar.xz archive. We can uncompress it with

$ tar xJf 2012-02-05@14h13.02.tar.xz

We see it contains:

.
├── changed
│   └── example1.xdelta3
└── deleted
    └── dir1
        └── document2

Under the deleted folder are all the files that were deleted. Under changed are the xdelta3 differences of the changed file.

To restore the old example1 to example1.restored, run:

$ xdelta3 -d -s example1 example1.xdelta3 example1.restored

Example: backing up a server via rsync over SSH

To create daily backups of a full server, execute:

$ crontab -e

and add the following line

@daily pachy my-server.com:/ /backups/my-server

This will create a full backup of all files. If you want to exclude some files, you can create a .pachy-filter file in the root of the server with, for instance:

- /proc
- /dev
- /sys
- /tmp
- /var/tmp
- /var/run
- /var/cache