snapshot is a simple Perl script used to manage ZFS snapshots. It is designed to be run from a cron job.

It's configuration file is assumed to be snapShot.yaml in the same directory as the script. For those of us who prefer perl data
structures, there is a script, confToYAML.pl which will take a perl definition of the configuration file and convert to yaml. Call 
it with
confToYAML.pl < snapShot.cfg > snapShot.YAML
A sample of snapShot.cfg is included.

NOTICE: this uses the perl module yaml-tiny to read the configuration file
   Debian Based Systems: apt install libyaml-tiny-perl
   BSD Systems: cpan -i YAML::Tiny

Every place that uses a frequency (ie, retention, frequency, slop) is expressed as a number of seconds. This should be an integer,
optionally followed by a space and a unit. hour, day, week, month and year are acceptable units.

== globals

TESTING - if non-zero (true), will print the commands that would be executed to /tmp/snapshot
slop - Number of seconds of slop allowed a cron job to determine if a new snapshot should be taken.
listingkeys - Headers from the output of zfs list and zfs list -t snapshot, so we know which column is which

There is no guarantee that cron and the timestamp embedded in the snapshot name will be exactly right. For example, if you were to
run the cron job every hour, you may be off by a minute or two when deciding to create a new snapshot. 'slop' allows for this by
saying "if we are slop seconds from needing a new snapshot, pretend we need it now". For a hourly cron job checking for daily 
snapshots, slop could be something like '1 hour'

== datasets

Basically, you choose one or more datasets to be managed. Each dataset can have three flags:

retention: How long a to keep a snapshot after it was created
frequency: How often to create a new snapshot
recursive: Adds the -r command to both zfs snapshot and zfs destroy commands if set to non-zero

The dataset key should be a regex, so escape all forward slashes and periods, ie for 
storage/iscsi.shares
you would use
storage\/iscsi\.shares
The regex must match the entire string to keep from matching storage/iscsi.shares/local_stuff, etc... If you want to match
child datasets, end the regex with '.*', ie
storage\/iscsi\.shares.*

See $config->{'datasets'}

== snapshots

Snapshots will be managed only if they match the parse regex, and will be created using the template string, which must be parsable 
by strftime. Care must be taken by the user to ensure parse and template match, and are correctly identified by parseFields.

See $config{'snapshot'}.