rsnapshot HOWTO

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2004-01-20

Revision History
Revision 1.0.0	2005-01-31	NR
Updated for rsnapshot 1.2.0
Revision 0.9.7	2005-01-17	NR
Spelling corrections submitted by Nicolas Kaiser
Revision 0.9.6	2004-12-13	NR
Misc. updates
Revision 0.9.5	2004-07-10	NR
Relicensed document under GPL, instead of FDL
Revision 0.9.4	2004-07-02	NR
Added description of proper crontab time settings
Revision 0.9.3	2004-06-11	NR
Misc. updates
Revision 0.9.2	2004-05-16	NR
Updated --link-dest info
Revision 0.9.1	2004-01-20	NR
Added --link-dest info
Revision 0.9	2004-01-10	NR
First draft

Abstract

rsnapshot is a filesystem backup utility based on rsync. Using rsnapshot, it is possible to take snapshots of your filesystems at different points in time. Using hard links, rsnapshot creates the illusion of multiple full backups, while only taking up the space of one full backup plus differences. When coupled with ssh, it is possible to take snapshots of remote filesystems as well. This document is a tutorial in the installation and configuration of rsnapshot.

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Table of Contents

The latest version of the program and this document can always be found at .

This document, rsnapshot HOWTO, is copyrighted (c) 2005 by Nathan Rosenquist. You can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. A copy of the license is available at .

No liability for the contents of this document can be accepted. Use the concepts, examples and information at your own risk. There may be errors and inaccuracies, that could be damaging to your system. Proceed with caution, and although this is highly unlikely, the author(s) do not take any responsibility.

All copyrights are held by their by their respective owners, unless specifically noted otherwise. Use of a term in this document should not be regarded as affecting the validity of any trademark or service mark. Naming of particular products or brands should not be seen as endorsements.

Feedback is most certainly welcome for this document. Send your additions, comments and criticisms to the following email address : <>.

I originally used Mike Rubel's shell scripts to do rsync snapshots a while back. These worked very well, but there were a number of things that I wanted to improve upon. I had to write two shell scripts that were customized for my server. If I wanted to change the number of intervals stored, or the parts of the filesystem that were archived, that meant manually editing these shell scripts. If I wanted to install them on a different server with a different configuration, this meant manually editing the scripts for the new server, and hoping the logic and the sequence of operations was correct. Also, I was doing all the backups locally, on a single machine, on a single hard drive (just to protect from dumb user mistakes like deleting files). Never the less, I continued on with this system for a while, and it did work very well.

This section will walk you through the installation of rsnapshot, step by step. This is not the only way to do it, but it is a way that works and that is well documented. Feel free to improvise if you know what you're doing.

If you've followed these instructions so far, you will have configured rsnapshot to be installed under /usr/local, with the config file in /etc. Under these circumstances, it will be necessary to become root to install the program. Now is the time to do so. You will, of course, need the root password to do this:

This will give you the complete documentation. However, it assumes that you already know what you're doing to a certain extent. If you just want to get something up and running, this tutorial is a better place to start. If your system can't find the man page, /usr/local/man probably isn't in your $MANPATH environmental variable. This is beyond the scope of this document, but if it isn't working for you, you can always read the newest man page on the rsnapshot web site at

In this example, we will be using the /.snapshots/ directory to hold the filesystem snapshots. This is referred to as the “snapshot root”. Feel free to put this anywhere you have lots of free disk space. However, the examples in this document assume you have not changed this parameter, so you will have to substitute this in your commands if you put it somewhere else.

What makes GNU cp so special is that unlike the traditional UNIX cp, it has the ability to make recursive “copies” of directories as hard links.

If you don't have GNU cp, there is a subroutine in rsnapshot that somewhat approximates this functionality (although it won't support more esoteric files such as device nodes, FIFOs, sockets, etc). This gets followed up by another call to rsync, which transfers the remaining special files, if any. In this way, rsnapshot can support all file types on every platform.

The cmd_du parameter specifies the path to the du program. du is a command line tool that reports on disk usage. rsnapshot uses du to generate reports about the actual amount of disk space taken up, which is otherwise difficult to estimate because of all the hard links.

If you have rsync version 2.5.7 or later, you may want to enable this. With link_dest enabled, rsnapshot relies on rsync to create recursive hard links, overriding GNU cp in most, but not all, cases. With link_dest enabled, every single file on your system can be backed up in one pass, on any operating system. To get the most out of rsnapshot on non-Linux platforms, link_dest should be enabled. Be advised, however, that if a remote host is unavailable during a backup, rsnapshot will take an extra step and roll back the files from the previous backup. Using GNU cp, this would not be necessary.

• You must have key-based logins enabled for the root user at example.com, without passphrases. If you wanted to perform backups as another user, you could specify the other user instead of root for the source (i.e. [e-mail]). Please note that allowing remote logins with no passphrase is a security risk that may or may not be acceptable in your situation. Make sure you guard access to the backup server very carefully! For more information on how to set this up, please consult the ssh man page, or a tutorial on using ssh public and private keys. You will find that the key based logins are better in many ways, not just for rsnapshot but for convenience and security in general. One thing you can do to mitigate the potential damage from a backup server breach is to create alternate users on the client machines with uid and gid set to 0, but with a more restrictive shell such as scponly.

• This backup occurs over the network, so it may be slower. Since this uses rsync, this is most noticeable during the first backup. Depending on how much your data changes, subsequent backups should go much, much faster since rsync only sends the differences between files.

With this parameter, the second column is the full path to an executable backup script, and the third column is the local path you want to store it in (just like with the "backup" parameter). For example:

Your backup script simply needs to dump out the contents of whatever it does into it's current working directory. It can create as many files and/or directories as necessary, but it should not put its files in any pre-determined path. The reason for this is that rsnapshot creates a temp directory, changes to that directory, runs the backup script, and then syncs the contents of the temp directory to the local path you specified in the third column. A typical backup script would be one that archives the contents of a database. It might look like this:

This tells rsnapshot to simulate an "hourly" backup. It should print out the commands it will perform when it runs for real. Please note that the test output might be slightly different than the real execution, but only because the test doesn't actually do things that may be checked for later in the program. For example, if the program will create a directory and then later test to see if that directory exists, the test run might claim that it would create the directory twice, since it didn't actually get created during the test. This should be the only type of difference you will see while running a test.

If you followed the instructions in this document, you should now have rsnapshot installed and set up to perform automatic backups of your system. If it's not working, go back and trace your steps back to see if you can isolate the problem.

The latest version of this document and the rsnapshot program can always be found at

Perl

GNU cp and du (coreutils package)

rsync

OpenSSH

rsnapshot