Introduction

A few days ago I wanted to start doing incremental backups from my laptop to my Raspberry Pi 2 running Alpine Linux. I’ve had used rdiff-backup for some years now and I’m really happy with it. rdiff-backup is similar to rsync, in the sense that lets you synchronize folders over the network, but it has two added nice features: when synchronizing, only the differences between the files that have changed are sent; and after every synchronization, the differences between the old version of the files and the new ones is kept. In other words, it keeps backwards in time incremental backups, allowing you to revert the files in time.

After trying to backup my Documents folder from my Debian laptop I encountered an error that was caused by an incompatibility between versions. Debian packages version 1.2.8 while Alpine packages version 1.3.3. I found this to be an odd decision for Alpine. Both versions were released in March 2009 and haven’t had any update since then. Version 1.2.8 is marked as stable whereas 1.3.3 is marked as development/unstable. I don’t know the internal differences between the two versions, but I checked other distributions like Arch and they also package version 1.2.8 instead of 1.3.3.

So, in order to get the version 1.2.8 in Alpine I took the easy route and installed it manually. After having done this, I realize that maybe it would have been much better to learn about the Alpine build system and build the package by reverting the commit that updated rdiff-backup from 1.2.8 to 1.3.3

Build and install

Anyhow, here’s how I installed rdiff-backup 1.2.8 manually:

We first install rdiff-backup dependencies plus the packages required to build rdiff-backup from source.

apk add librsync
apk add gcc librsync-dev python-dev musl-dev patch

We download the sources of rdiff-backup-1.2.8, check the hash sum to verify that we got it right and we extract them.

mkdir tmp
cd tmp/
wget http://savannah.nongnu.org/download/rdiff-backup/rdiff-backup-1.2.8.tar.gz
[ "0d91a85b40949116fa8aaf15da165c34a2d15449b3cbe01c8026391310ac95db" \
    = $(sha256sum rdiff-backup-1.2.8.tar.gz | cut -d " " -f 1) ] && echo OK
tar xzf rdiff-backup-1.2.8.tar.gz

Then we download the required patch to build rdiff-backup with librsync-1.0.0, in this case, from the Arch package git repository. We check the patch and apply it.

wget https://git.archlinux.org/svntogit/community.git/plain/trunk/rdiff-backup-1.2.8-librsync-1.0.0.patch?h=packages/rdiff-backup \
    -O rdiff-backup-1.2.8-librsync-1.0.0.patch
[ "a00d993d5ffea32d58a73078fa20c90c1c1c6daa0587690cec0e3da43877bf12" \
    = $(sha256sum rdiff-backup-1.2.8-librsync-1.0.0.patch | cut -d " " -f 1) ] && echo OK
cd rdiff-backup-1.2.8/
patch -Np1 -i ../rdiff-backup-1.2.8-librsync-1.0.0.patch

We are ready to build rdiff-backup and install it in the system.

python setup.py build
python setup.py install --prefix=/usr --root=/

We must not forget to add the newly installed files in the local backup database, so that they are stored permanently. I deliberately skip the docs.

lbu add /usr/lib/python2.7/site-packages/rdiff_backup* /usr/bin/rdiff-backup*

After we are done, we can remove the packages we used to build rdiff-backup.

apk del gcc librsync-dev python-dev musl-dev patch

Now rdiff-backup works correctly from my Debian laptop to my Alpine Raspberry Pi :)