Simple versioned TimeMachine-like backup using rsync
Using TimeMachine with rsync: Over many years, I have dealt with scripts that do backup versioning, i.e., maintain multiple backups. Due to their flexibility, they have been complex to understand and configure. Here is a simple rsync-based tool with a different focus: The experienced systems administrator who wants to keep his system’s complexity down.
Backup in action: TimeMachine and rsync
It consists of a simple script, which you can call rsync-backup.sh and store wherever you like, e.g., in /usr/local/sbin. I will use these names and paths in the examples.
#!/bin/sh
# Usage: rsync-backup.sh <src> <dst> <label>
if [ "$#" -ne 3 ]; then
echo "$0: Expected 3 arguments, received $#: $@" >&2
exit 1
fi
if [ -d "$2/__prev/" ]; then
rsync -a --delete --link-dest="$2/__prev/" "$1" "$2/$3"
else
rsync -a "$1" "$2/$3"
fi
rm -f "$2/__prev"
ln -s "$3" "$2/__prev"During normal operation, it boils down to three simple statements:
rsyncwith--link-dest: Copying the contents of <src> to <dst>/<label>, reusing the files from the previous backup with hard links ((The non---link-destrsyncdoes not use--deleteto reduce the risk of accidentally deleting files when called with wrong parameters))rmandln: Remember this backup location for the next incremental backup.
Voilà – it doesn’t get much easier than that!
Of course, there is something missing: The actual backup policy. It is separated into cron, which I consider an advantage. Using this separation of duties, many policies can be implemented very easily and composed in a modular way:
Create daily backups for every weekday
You might know this from automysqlbackup or autopostgresqlbackup: A backup is created every day and overwritten after 7 days. This is achieved by adding the following file to /etc/cron.daily/:
#!/bin/sh /usr/local/bin/rsync-backup.sh /home /data/backup `date +%A`
All your user’s files are copied daily to /data/backup, named after the current day, overwritten weekly.
Daily backups for a month
Sure, this is easy as well, by putting this with a descriptive name into/etc/cron.daily/:
#!/bin/sh /usr/local/bin/rsync-backup.sh /home /data/backup `date +Day-%d`
