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A simple backup program in python with an emphasis on data integrity and transparent behaviour

Project description



  • Install the latest release from PyPI (supports all platforms with Python and has no dependencies outside the standard library)
pip install backupy --upgrade


  • Backup, Mirror, and Sync Modes
  • Compare files using attributes or CRCs
  • View changed file tree with curses
  • Detection and alerts of corrupted files
  • Detection and alerts of unexpected file modifications on destination outside of backups and mirrors, or sync conflicts (a file was modified on both sides since the last sync)
  • JSON formatted database for tracking files and CSV formatted logs
  • Filter files with regular expressions
  • Files are always safe by default, being moved to an identically structured archive directory before being deleted or overwritten

Design Goals

  • Backups should be future proof and verifiable, even without BackuPy
  • Code should be simple and easy to verify to ensure predicable and reliable operation
    • a callgraph is available in analysis/callgraph.svg
    • there are only three, easy to follow functions (under FileManager in backupy/ that ever touch your files, no more, no less, three shall be the number of thou functions, and the number of the functions shall be three
    • use trustworthy dependencies
  • Follow the principle of least astonishment
    • clear backup behaviour between directories, the current status of files and how they will be handled upon execution should be perfectly obvious
  • Avoid feature creep and duplicating other programs
    • no delta-transfer (extend with another backend)
    • no network storage or FUSE support (these must be mounted by another program for BackuPy to see them)
    • no backup encryption (use encrypted storage)
    • no filesystem monitoring (this is not a continuous backup/sync program)
  • Easily extensible with other backends
    • all the low level functions used for file operations are under FileOps from backupy.utils for easy monkey patching (see

Usage Description

  • Source and destination directories can be any directory accessible via the computer's file system
    • Destination can be empty or contain files from a previous backup (even one made without BackuPy), matching files on both sides will be skipped
    • Use the --posix flag if you plan on using BackuPy between Windows and any other OS
  • Main modes (how to handle new and deleted files)
    • Backup mode: copies files that are only in source to destination
    • Mirror mode: copies files that are only in source to destination and deletes files that are only in destination
    • Sync mode: copies files that are only in source to destination and copies files that are only in destination to source
      • you may also want to use --sync-delete to propagate deletions
      • see write_database_x2 in the configuration file if syncing more than two folders
  • Selection modes (which file to select in cases where different versions exist on both sides)
    • Source mode: copy source files to destination
    • Destination mode: copy destination files to source
    • Newer mode: copy newer files based on last modified time
    • None mode: don't copy either, differing files will only be logged for manual intervention
  • Compare modes (how to detect which files have changed)
    • Attribute mode: compare file attributes (size and last modified time)
    • Attribute+ mode: compare file attributes and calculate CRCs only for new and changed files for future verification
    • CRC mode: compare file attributes and CRC for every file, and checks previously stored CRCs to detect corruption
      • you may also want to use --verify to verify the CRC of files after they're copied
  • Test your options first with the --dry-run flag
  • See Command Line Interface and Configuration File below for all available options
  • By default, you will always be notified of any changes, unexpected modifications, sync conflicts, or file corruption before being prompted to continue, cancel, or skip selected files
    • it is recommended to use --qconflicts if using --noprompt, especially if also using --noarchive
  • By default, you will be prompted before any changes are made to your files and
    • overwritten files will be moved to <source|dest>/.backupy/Archives/yymmdd-HHMM/<original path>
    • deleted files will be moved to <source|dest>/.backupy/Trash/yymmdd-HHMM/<original path>
  • Symbolic links to folders are never followed and always copied verbatim
  • Symbolic links to files are followed by default, copying the referenced file, use --nofollow to copy symbolic links to files verbatim
  • To restore files, just copy them over from your destination to source (or swap source and destination in BackuPy)

Command Line Interface

usage: backupy [options] -- <source> <dest>
       backupy <source> <dest> [options]
       backupy <source> --load [-c mode] [--dbscan] [--dry-run]
       backupy -h | --help | --version

positional arguments:
  source       Path to source
  dest         Path to destination

optional arguments:
  -h, --help   show this help message and exit
  --version    show program's version number and exit

file mode options:

  -m mode      Main mode: for files that exist only on one side
                 MIRROR (default)
                   [source-only -> destination, delete destination-only]
                   [source-only -> destination, keep destination-only]
                   [source-only -> destination, destination-only -> source]
  -s mode      Selection mode: for files that exist on both sides but differ
                 SOURCE (default)
                   [copy source to destination]
                   [copy destination to source]
                   [copy newer to opposite side]
                   [do nothing]
  -c mode      Compare mode: for detecting which files differ
                 ATTR (default)
                   [compare file attributes: mod-time and size]
                   [compare file attributes and record CRC for changed files]
                   [compare file attributes and CRC for every file]

misc file options:

               Use the database to propagate deletions since the last sync
  --fi regex [regex ...]
               Filter: Only include files matching the regular expression(s)
               (include all by default, searches file paths)
  --fe regex [regex ...]
               Filter: Exclude files matching the regular expression(s)
               (exclude has priority over include, searches file paths)
  --noarchive  Disable archiving files before overwriting/deleting to:
  --nofollow   Do not follow symlinks when copying files
  --nomoves    Do not detect when files are moved or renamed

execution options:

  --noprompt   Complete run without prompting for confirmation
  -d, --dbscan
               Only scan files to check and update their database entries
  -n, --dry-run
               Perform a dry run with no changes made to your files
  -q, --qconflicts
               Quit if database conflicts are detected (always notified)
                 -> unexpected changes on destination (backup and mirror)
                 -> sync conflict (file modified on both sides since last sync)
                 -> file corruption (ATTR+ or CRC compare modes)
  -v, --verify
               Verify CRC of copied files

backend options (experimental):

  --cold       Do not scan files on destination and only use local databases
  --rsync      Use rsync for copying files

configuration options:

  --nolog      Disable writing log and file databases to:
  -p, --posix  Force posix style paths on non-posix operating systems
  -k, --save   Save configuration to <source>/.backupy/config.json and exit
  -l, --load   Load configuration from <source>/.backupy/config.json and run

BackuPy is a simple backup program in python with an emphasis on data 
integrity and transparent behaviour - 

BackuPy comes with ABSOLUTELY NO WARRANTY. This is free software, and you are 
welcome to redistribute it under certain conditions. See the GNU General 
Public Licence for details.

Configuration File

  • The config file is saved to, and loaded from <source>/.backupy/config.json
    • it contains all the options from the command line interface along with some additional options
    • the only CLI options that can be used with --load and can override settings in config.json are -c mode, --dbscan, and --dry-run
      • the overrides can enable --dbscan or --dry-run but not disable
    • see backupy/ for where all the options and defaults are stored in code
    • below is a description of all the other options that are available
  • source_unique_id & dest_unique_id
    • unique id for each folder, used when write_database_x2 is enabled, each assigned a random string by default
  • archive_dir = ".backupy/Archive"
    • can be any subdirectory
  • config_dir = ".backupy"
    • can't be changed under normal operation
  • log_dir = ".backupy/Logs"
    • can be any subdirectory
  • trash_dir = ".backupy/Trash"
    • can be any subdirectory
  • cleanup_empty_dirs = True
    • delete directories when they become empty
  • root_alias_log = True
    • abbreviate absolute paths to source and dest with <source> and <dest> in logs
  • stdout_status_bar = True
    • show progress status bar
  • verbose = True
    • print list of differences between directories to stdout
  • write_database_x2 = False
    • write both source and destination databases to each side using their unique_id, useful for syncing groups of more than two folders or with the --sync-delete flag
  • write_log_dest = False
    • write a copy of the log to <dest>/<log_dir>/log-yymmdd-HHMM-dest.csv
  • write_log_summary = False
    • alternative log structure, written in addition to standard log
  • nocolour = False
    • disable colour when printing to stdout

Building From Source

  • Run tests with
python test
  • Building a python package
python sdist
  • Building an executable with the GUI (depends on Gooey) (deprecated, may rewrite with flutter)
pyinstaller build.spec
  • You can package the executable on Windows by running setup.iss with Inno Setup

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