insnapshot

A bash script that watches a directory and automatically creates a snapshot of it when the content changes

Warning

This script is in very early stages of development.

Usage

insnapshot [OPTION...] [SRC] [DEST]

Watches the SRC directory for changes and creates snapshots under the DEST
directory. If SRC is omitted, the current working directory is used. If DEST
is omitted, it will be set to /old-versions.

Options:

  --exclude-from=FILE        File specifying exclude patterns passed to rsync,
                             see there [default: /home/schooft/.rsync/exclude]
  --wait=SECONDS             Wait until there are no changes for the specified
                             number of seconds [default: 2]
  --max-wait=SECONDS         When there are ongoing consecutive, rapid changes,
                             wait at most this number of seconds [default: 300]
  --min-interval=SECONDS     Minimum duration between two snapshots in seconds
                             [default: 900]
  --max-size=SIZE            Don't baclup any file larger than SIZE, see rsync
                             [default: ]
  --oneshot                  Make a snapshot immediately and exit
  -h, --help                 Print help and exit
  --version                  Print version and exit

How does it work

insnapshot utilizes inotifywatch to be efficiently notified on any changes in the watched directory. It then waits until there are no changes for a few seconds to combine rapid consecutive changes (but it waits at maximum a few minutes) and then calls rsync to create a snapshot in the target directory und the currect date and time. It then sleeps for some time to keep the number of snapshots reasonable.

The --link-dest option of rsync allows for space efficient storage as unchanged files are simply hard linked to the previous snapshot. Nevertheless, each snapshot appears as a full copy of the source directory, allowing for easy recovery of old versions.

Requirements

• inotifywait
• rsync

In addition, the file system of the target directory must support hard links.

To run the tests, the following must be installed as well:

• tree

Limitations

• A snapshot state can be inconsistent if changes happen during a backup

Contributing

Please feel free to open issues or pull requests.

Acknowledgments

This script was inspired by gitwatch and rsync time machine.