ZFS diff

PSARC/2010/105:

        There is a long-standing RFE for zfs to be able to describe
        what has changed between the snapshots of a dataset.
        To provide this capability, we propose a new 'zfs diff'
        sub-command.  When run with appropriate privilege the
        sub-command describes what file system level changes have
        occurred between the requested snapshots.  A diff between the
        current version of the file system and one of its snapshots is
        also supported.

        Five types of change are described:

        o    File/Directory modified
        o    File/Directory present in older snapshot but not newer
        o    File/Directory present in newer snapshot but not older
        o    File/Directory renamed
        o    File link count changed

      zfs diff snapshot  snapshot | filesystem

         Gives a high level description of the differences between a
         snapshot and a descendant dataset.  The descendant may either
         be a later snapshot of the dataset or the current dataset.
         For each file system object that has undergone a change
         between the original snapshot and the descendant, the type of
         change is described along with the name of the file or
         directory.  In the case of a rename, both the old and new
         names are shown.

         The type of change is described with a single character:

         +   Indicates the file/directory was added in the later dataset
         -   Indicates the file/directory was removed in the later dataset
         M   Indicates the file/directory was modified in the later dataset
         R   Indicates the file/directory was renamed in the later dataset

        If the modification involved a change in the link count of a
        file, the change will be expressed as a delta within
        parentheses on the modification line.  Example outputs are
        below:

         M       /myfiles/
         M       /myfiles/link_to_me   (+1)
         R       /myfiles/rename_me -> /myfiles/renamed
         -       /myfiles/delete_me
         +       /myfiles/new_file