Multiplicity is a very basic frontend to rdiff-backup. Its goal is to provide easy management of multiple independant backup tasks.


rdiff-backup uses rsync (incremental file tree copies to save bandwidth), hard links (to save backup space), ssh (to transmit data) and a very handy incremental machinery (to allow us to go back in time through our backups).

multiplicity is a script aimed at easing the management of backup jobs. It is a basic frontend to rdiff-backup. It consists of the main scipt and a directory filled with task files. Each task file defines a backup source, a backup target and various other parameters.

Task files

A task file must be in the configuration directory (may be set on the command line and defaults to /etc/multiplicity). It should be named with a .task suffix (read dot task). The following configuration values are accepted in a task file :

  • run_this : This globally enables or disables the task file. Any value other than yes disables the task file.
  • max_age : delete files deleted more than this value ago and file history older than this value. This parameter is directly passed to rdiff-backup.
  • source_root : the root directory of the files you want to backup.
  • target_root : the root directory where you want to backup your files.
  • include_file : a full path (or relative to the configuration directory) to a file that lists what files to include in the backup. As the default is to backup all files, this is only usefull if the files you list here would have been excluded regarding the exclude_file configuration. See next dot.
  • exclude_file : files to exclude from the backup.
  • pre : execute this in the bash shell before executing the backup task. This must fit on one line.
  • post : execute this after the backup task. This must fit on one line.

Example task file /etc/multiplicity/example.task :

run_this        no
max_age         185D
source_root     /
target_root     /backup
exclude_file    local.exclude
pre             mount -o remount,rw /backup
post            mount -o remount,ro /backup

Carefull, what separates configuration keys from configuration values is a real tabulation \t. I should probably fix this, one day.

Example exclude file /etc/multiplicity/local.exclude :


Global pre and post scripts

There is also the possibility of running global pre and post scripts, i.e scripts that run before and after the task batch. Those are to put in the configuration directory under the names of pre.sh and post.sh.

Example pre.sh :

# This script is run before the backup task batch begins.
# Feel free to customize it

# Dump mysql data to a file
mysqldump --user root --password=pass --all-databases > /var/backups/mysqldata base.dump


multiplicity accepts the following command-line options :

  • -cconfdir : Specify confdir as the configuration directory, i. e. where to look for task files.
  • -v : Be verbose. Default is really quiet.
  • -h : Display a (very) short help summary.


You can browse multiplicity's source online or grab a snapshot archive on the same page.

You can get the source using git:

$ git clone http://sousmonlit.zincube.net/~niol/repositories.git/multiplicity

Installation (short)

multiplicity may run in any directory, but it was made to be run in the following way :

  • Create the directory /etc/multiplicity and create task files. You can re-use the example from the distribution.
  • Drop the multiplicity script in a cron directory if applicable, for example on Debian, I dropped it in /etc/cron.daily to make it run once a day. After a couple of days, you may want to put VERBOSE to a zero value to stop getting cron report emails.

Installation (my setup)

This section describes my setup. The goal is to backup from ripley to backup1 and backup2.

Password-less SSH logins

The first thing to do is to setup password-less SSH logins for the root user to the hosts you want to backup to (or the hosts you want to backup from, but I'll describe here how to use remote backup hosts to backup to). First create a key pair for this purpose.

# cd
# mkdir .ssh
# chmod 700 .ssh
# ssh-keygen -t rsa -f ~/.ssh/id_rsa
(no passphrase)

If, like me, you have aliases for your hosts and special ports, you may want to use a .ssh/config file :

Host backup1
User backupuser
Port 400
HostName backupfool.foo1.org

Host backup2
User backupuser
Port 400
HostName backupguy.foo2.org

Now, copy your IDs to the remote hosts (repeat for backup2) :

# ssh-copy-id -i ~/.ssh/id_rsa.pub backupuser@backup1

Now you should be able to login with the local root user on localhost:

# ssh backup1
(no password prompted)
backupuser@backupfool.foo1.org $

Multiplicity configuration

So, here is the plan : I want to backup several selected directories to a dedicated /backup partition and I want to backup only a part of those selected directories to the remote hosts, especially avoiding to send to the remote hosts my passwords and my emails.

I run a mySQL server on ripley. Thus, I use /etc/multiplicity/pre.sh to dump the database contents to a file :

mysqldump --user root --password=unbreakable_password --all-databases > /var/backups/mysqldatabase.dump

Then I described /etc/multiplicity/local.include which is a list of the things on ripley that I want to backup :

- **tmp
- /var/fileserv/enac/album**tn
- **

Basically, I want to backup /etc, no files that end with tmp, my personal directory, stuff on my ftp server except thumbnails directories, /var/backups, my mailing list manager config, my web directory and nothing else. Check the backup-manager manual page for more information on file inclusions and exclusions (globbing filelists).

But when backing up to a remot host, I want to omit some files (the contents of the ftp server which is too big and the ones that contain clear text passwords) which I described in /etc/multiplicity/remote.exclude:


(I really don't like clear-text-stored passwords…)

This was the most difficult part bescause you need to know what is on your computer. But now, the only remaining thing is to describe multiplicity tasks.

/etc/multiplicity/local.task (the local backup):

run_this        yes
max_age         185D
source_root     /
target_root     /backup/local
include_file    local.include
pre             mount -o remount,rw /backup
post            mount -o remount,ro /backup

/etc/multiplicity/backup1.task (the order of exclude_file and include_file is important):

run_this        yes
max_age         10D
source_root     /
target_root     backup1::/home/backupuser/fromripley/
exclude_file    remote.exclude
include_file    local.include

/etc/multiplicity/backup2.task (this is the second friend I send my backups to, just in case):

run_this        yes
max_age         10D
source_root     /
target_root     backup2::/home/backupuser/fromripley/
exclude_file    remote.exclude
include_file    local.include

This should be self explainatory and this should show what is multiplicity about.

Running the script

The first run should be a bit long :

# /etc/cron.daily/multiplicity -v

From now on, you can check on the remote hosts which files have been backed up :

# ssh backup1
backupuser@backupfool.foo1.org $ ls fromripley
etc  home  rdiff-backup-data  root  var

You also may check what increments are available :

backupuser@backupfool.foo1.org $ rdiff-backup -l fromripley
Found 9 increments:
    increments.2005-12-27T06:30:54+01:00.dir   Tue Dec 27 06:30:54 2005
    increments.2005-12-28T06:31:53+01:00.dir   Wed Dec 28 06:31:53 2005
    increments.2005-12-29T06:31:03+01:00.dir   Thu Dec 29 06:31:03 2005
    increments.2005-12-30T06:32:27+01:00.dir   Fri Dec 30 06:32:27 2005
    increments.2005-12-31T06:33:26+01:00.dir   Sat Dec 31 06:33:26 2005
    increments.2006-01-01T06:32:10+01:00.dir   Sun Jan  1 06:32:10 2006
    increments.2006-01-02T06:31:25+01:00.dir   Mon Jan  2 06:31:25 2006
    increments.2006-01-03T06:30:41+01:00.dir   Tue Jan  3 06:30:41 2006
    increments.2006-01-04T06:31:11+01:00.dir   Wed Jan  4 06:31:11 2006
Current mirror: Thu Jan  5 06:31:08 2006

Check the rdiff-backup beginners guide to know how to recover an old file…