Chapter 1. Introduction


Dar is an extremely versatile and powerful tool and DarGUI is not planned to be a means of accessing all its features. Instead, DarGUI is intended to simplify the most common tasks of making backup archives and restoring files from these and to provide a small number of additional features. DarGUI provides the following features:

Many of these descriptions are copied from Denis Corbin's FEATURES document.

DarGUI is able to backup everything from a single file to an entire filesystem. Additionally a mechanism of filters enables the inclusion or exclusion of individual files or directories while backing up or restoring a directory tree. (back to top)
Differential backup
When making a backup with DarGUI, you have the option of making a full backup or a differential backup. A full backup, as expected, makes a backup of all files as specified on the command line (with or without filters). A differential backup, however, saves only files that have changed since a given reference backup. Additionally, files that existed in the reference backup and which do not exist anymore at the time of the differential backup are recorded in the backup. At recovery time, (unless you deactivate it), restoring a differential backup will update changed files and new files, but also remove files that have been recorded as deleted. Note that the reference backup can be a full backup or another differential backup. This way you can make a first full backup, then many differential backup, each taking as reference the last backup made. (back to top)
DarGUI can split an archive over several removable media whatever their number is and whatever their size is. Archives produced by  DarGUI can be saved onto floppy disk, CD-R, DVD-R, CD-RW, DVD-RW, Zip, Jazz, etc... Given the desired size, Dar will split the archive into several files (called SLICES). DarGUI can also backup data to one slice of any size. When restoring files, DarGUI will simply pause and prompt the user for the location of a missing slice.
It is important to remember, however, that older versions of dar need to be able to examine both the first and last slices of a set in order to get a listing of its contents.  For this reason, when storing archives on DVD, CD or similar media consider using the method described in the note about using slices.  (back to top)

DarGUI can use compression using the gzip, bzip2, lzo or xz algorithms. Note that compression is done before slices are created, which means that using compression with slices will not make slices smaller, but will probably result in the backup being contained in fewer slices. (back to top)
Selective compression
DarGUI can be use filters to determine which files will be compressed. This way you can speed up the backup operation by not trying to compress *.mp3, *.mpg, *.zip, *.gz and other already compressed files. Another setting allows you to prevent files under a given size (whatever their name), from being compressed. (back to top)
Direct access
Even using compression Dar does not have to read the entire backup to extract one file. This way if you just want to restore one file from a huge backup, the process will be much faster than using tar. Dar first reads the catalog (i.e. the contents of the backup), then it goes directly to the location of the saved file(s) that you want to restore and extracts them. When using slices Dar will ask only for the slice(s) containing the file(s) to restore. (back to top)
Archive testing
thanks to CRC (cyclic redundancy checks), Dar is able to detect data corruption in the archive. If data corruption occurs in a file it will not be possible to restore it but the other files in the archive can be restored even when compression is used. (back to top)
Archive encryption
Dar archives can be encrypted using the Blowfish cypher. (back to top)
The catalog (i.e.: the contents of an archive), can be extracted (this operation is called isolation) to a much smaller file. This catalog can in turn be used as reference for making a differential archive. This means that there is no need to be able to examine an original archive to be able to create a differential backup from it. Only its catalog is necessary. (back to top)
Restore individual files
You can restore any combination of individual files and directories by selecting them in the tree-view display. DarGUI's selection tools make it possible to select all files with a particular suffix or with a particular pattern in their name. For example all files in an archive ending in .html can be easily selected for restoration. (back to top)
Flat restoration
It is possible to restore any file without restoring the directory tree that it was in at the time of the backup. If this option is enabled, all files will be restored in the root directory whatever their original location was. (back to top)
Pause between slices 
Dar can be instructed to pause once a slice has been written. This feature can be used to enable writing to CD between slices, for example. (back to top)
Timestamp archive names
DarGUI can automatically include the date and time of creation in the name of a DAR archive. (back to top)
Scheduled backups 
DarGUI can schedule a backup script to be run at a specified time once only or regularly. (back to top)
Write backup scripts 
DarGUI can produce Dar backup scripts which can be used independently of DarGUI. (back to top)
Track file versions 
DarGUI can maintain a database of files held in archives, to make it easier to locate a specific version of a file. (back to top)