backup-copy

backup-copy(1) is my backup script. It allows me to save a snapshot of my filesystem every day (or every minute, if I wanted to) with the complete tree of files saved every time - all at a cost of not more than about 2Mb/backup. The backup is mirrored on another file system, either local or remote (using ssh(1)). The backup directory looks like this:

.../backup-copy/hostname/2009/01/28-21_51
                          .../01/29-21_51
                          .../01/30-21_51
                          .../01/31-21_51
                          .../02/01-21_51

In other words, one directory per backup named with the date and time of the backup. This is done with rsync(1)'s wonderful ability to hard-link across directory trees - each file in each directory is hard-linked to the same file in the prior directory. Only files that have changed actually get a new file saved there.

The result is a tree of backups which are all copies of the source files at the time of backup - but only the changes 'cost' me in disc space and network bandwidth.

Some consequences:

• this is disc-to-disc backup, rather than tape or DVD - no reason why you can't save the backup directory to tape or DVD, of course.
• this really works well when the changes are in small files rather than small changes in huge files - the unit of discrimination is the file
• there is no compression involved (unless, of course, your destination disc is mounted as a compressed disc eg using fuse(8))

Usage (in lieu of a man page!!)

backup-copy(1) needs an init file to direct the backup. The sample here .backup-copy.sample should give you an idea what to do.

• Don't forget the space character at the end of every INCLUDE and EXCLUDE string - it is essential.
• The init file should live in the user's home directory and must be named .backup-copy.hostname with 'hostname' being the name of the system that is being backed up (without any dots or domainname).
• The init file can contain a default destination but you can over-ride that on the command line. If you nominate eg. '/var' as the destination then a directory called /var/backup-copy/HOSTNAME must exist - otherwise backup-copy(1) assumes you've made an error in the name of the destination directory and stops. You can force it to create that new directory with the -i option.
• If you want to ensure the backup is always run by root (in case you forget) there is a flag to specify that in the init file.
• The EXCLUDE strings can use rsync(1)'s ** wildcard which means any directory - see the rsync(1) man page for full details.

Remote backups

To use a remote destination just use the usual ssh(1) syntax eg surfers:/var. It's generally a good idea to push your ssh key to the remote machine otherwise you have to constantly provide a password - and you can't do that in unattended jobs eg in a crontab(1) job.

Downloads

• backup-copy itself
• .backup-copy.sample is a sample init file
• backup-copy usage
• process-getopt is needed as for most of my scripts process-getopt doco