Product SiteDocumentation Site

Chapter 3. Technical Information

3.1. Backup formats
3.1.1. Archive/tar backups
3.1.2. Direct Copy/rsync backups
3.1.3. Minimum storage requirements
3.2. Preservation of file ownership and other attributes
3.3. Expected levels of reliability
3.4. Application data & logging
3.5. Command-line interface

3.1. Backup formats

This section details how fwbackups create backups and each type of backup's storage requirements.

3.1.1. Archive/tar backups

Archive backups use one of two methods to create the backup archive depending on the operating system. On Unix-like operating systems such as Linux, Unix and OS X, the tar executable is called upon directly to create a standard GNU tar archive, optionally with gzip or bzip2 compression. On Windows, Python's tarfile module is used to create a standard GNU compliant tar archive. In either case, backup compression is applied on-the-fly without the need for the tar archive to be created first.
Because the backup is in the format of a standard tar archive, should fwbackups ever fail to restore a backup any utility supporting the tar format such as GNOME's integrated file-roller utility or 7-zip on Windows may be used to extract files from the backup. For those confortable with the command line, a simple tar xfz <backup file> will extract all files from the backup.

3.1.2. Direct Copy/rsync backups

As with Archive backups, Direct copy backups will use one of two methods to copy files depending on the operatng system. On Windows, fwbackups uses a slightly modified version of the Python shutil library to copy files and folders. On Unix-like operating systems (Linux, Unix and OS X) fwbackups determines the appropriate parameters and then makes a call to rsync to copy the files (rsync is faster than shutil and therefore is used when the OS supports it). Thus, in either case the result is a direct copy of the files and folder structure.
Because files have been copied directly, if fwbackups fails to restore your files simply copying them from the backup destination to their desired location via drag-and-drop in your file browser will suffice.

3.1.3. Minimum storage requirements

Depending on your backup format and destination, the minimum storage requirements to complete a backup may change.
For local backups, both the Archive and Direct copy backup engines will copy files from the disk source to the destination without the need for temporary storage, even if compression is enabled. Therefore, you should have no problems backing up a full disk so long as your destination is on another volume such as USB or removable storage.
Backups to remote destinations have different storage requirements. Archive backups with a remote destination create the archive locally and then upload it via SFTP to the remote host. Therefore, you must have free space equal to the size of the files being backed up (unless compression is enabled, in which case slightly less would be required). In a Direct copy backup with a remote destination, files are uploaded directly to the remote machine and therefore it is possible to backup a full drive. However, be warned that a remote direct copy is significantly slower than a archive backup.