= Introduction

Dated Backup is a program which does exactly what it's name says: 
It creates backups of any directory, timestamping the backups. It then 
performs incremental backups on every subsequent run.  The really nice thing here 
is that those backups are fully viewable as snapshots, even though they are 
also incremental.

This method of backup uses the hard-link technique in combination
with rsync.  For more information on this technique, see: 

  http://www.mikerubel.org/computers/rsync_snapshots/
  
At the moment, this program can be thought of as a limited, Ruby version of
the popular unix utility rsnapshot.  Dated Backup's feature set already does
things a little different from rsnapshot, and in the future will diverge widely.
  
Dated Backup no longer depends on GNU cp, but instead uses rsync's --link-dest
option to simulate the hard-link method.


== Backup Assumptions

  * Your backup *server* is POSIX compliant (a modern day UNIX - Linux, *BSD, Mac OS X)
  * You would like to perform incremental snapshots with timestamps

= Installation:

  * sudo gem install 'dated_backup' --include-dependencies

== Dependencies

Dated Backup has the following dependencies:

  * Ruby
  * Rubygems
  * Rails' 'ActiveSupport' gem
  * A copy of rsync, which supports the --link-dest option (version 2.5.7 or greater).
  * A POSIX-like (Linux, BSD*, Mac OS X, Solaris) OS to store the backups  

Rsync is not required on the machine to be backed up - only on the machine which stores
the backup.  


= HOWTO Backup with Dated Backup

Each backup source will correspond to a configuration file, which defines the source 
directory (or remote location), and the local destination directory.  These two 
parameters are the only requirements for a backup configuration file to be valid.  
The script can be run with the executable dbackup:

<tt>$ dbackup my_script</tt>

Other scripts can be run sequentially by listing them in order:

<tt>$ dbackup my_first_script my_second_script</tt>

All of the configuration occurs in the configuration file.


== The DSL, or How To Write A Configuration File

Here are the valid key words which can be set in the main section of the configuration file:

  * source
  * sources
  * destination
  * options
  * user_domain
  
The values for these should be strings.  They are specified like so:

  source '/etc'
  
Multiple values can also be given:

  sources '/etc', '/home'
  
The destination keyword only takes one value, but in the next release (0.3), this should
be fixed to allow backups to be copied to multiple locations.

The 'source' (or 'sources') keyword and the 'destination' keyword
are the only ones needed for a valid backup config file.  The 'user_domain' keyword is used 
when the source is not a local directory (or local file).  The user_domain should be in user@server
style.  As for the 'options' keyword, this should be specified as a string for extra options to be
feed into rsync.  It too, is optional.


=== Before and After Filters

It is very convenient, and often necessary to perform something before or after a backup script
runs.  Any actions must be inside a 'before' or 'after' block:
  
  before do
    # ...some before action here
  end

  after {
    # ...some other action here
  }

You have the pick of do...end, or { ... }, thanks to Matz.  No doubt, this will be familiar to any
Ruby programmer.

At the time of this release (0.2), there is only one valid action - 'remove_old'.  Other actions, such
as running a script (or any number of scripts, in sequence), as well as running a command specified 
in the configuration file itself, should be coming in subsequent releases.

For some example configuration files, see the examples bundled with RDoc, or in the example_configs
directory.


=== remove_old

The remove_old block takes several different natural language time forms.  All of the statements inside
a remove_old block must begin with 'keep'.  An example would work best to illustrate how to use this:

  after do
    remove_old do
      keep this months backups
      keep last months backups
      keep monthly backups
    end
  end

This says the following: After the backup runs, remove all backups that do not conform to the criteria
given.  The first line will save all backups which have occured this month, regardless of what time 
they occurred (as long as they occurred in the current month).  The next line says the same, except for
last month's backups.

The last line, "keep monthly backups", will keep one backup from each month not already kept.  If you perform
daily backups every day, this would end of keeping the last day's backup from every month (the 29, 30, or 31,
according to the month)

A few things should be notice here: These config files read very easily, so don't let them fool you.  
They will delete your backups, forever lost.  I've already burned myself with the following: 

  after {
    remove_old {
      keep this weeks backups 
      keep last weeks backups 
      keep weekly backups from this month # or: keep this months weekly backups
      keep monthly backups # or: keep all monthly backups
    }
  }

After a month of backups, the month rolled over, and the next backup on the first of the month deleted
all backups, except the one just performed, and the one from the last day of the month before.  
So beware, and think before you specify any remove_old block at all.  

Another thing to notice (for any of you non-ruby programmers out there): The config file must be in valid
ruby, so specifying a "week's backups" should be written as a 'weeks backups', 
i.e., don't put any apostrophes in there.

The config file shown above should give you some hints on the possibilities.  Here are the valid keywords:

  Time specifiers:
    * this
    * last
  Time ranges (these can also be pluralized):
    * day 
    * month
    * week
    * year
  Incremental time slices (one per * methods):
    * daily
    * weekly
    * monthly
    * yearly
  And some placeholders, which have no affect, but allow the file to read nicely:
    * backup
    * backups
    * from
    * all

Some other keywords, such as 'yesterday', and 'today' will be added in subsequent releases.

And finally, a warning: If a remove_old block is given, but no keep rules are given, every backup
will be deleted!  This may change in a subsequent release, but for now, beware!


= Specifications / Tests

The rspec specdoc can be found here:

http://datedbackup.rubyforge.org/rspec_report.html

Rcov Coverage can be found here:

http://datedbackup.rubyforge.org/rcov/index.html


= License

Dated Backup is dual licensed under the GNU GPL as well as the MIT license.  This means that you 
can apply the license you so choose when you obtain this software.

= Contributions

If you are interested in contributing code or documentation, or would like to see a feature
please submit these via the Rubyforge tracker at 

http://rubyforge.org/projects/datedbackup/