Archive bit

The archive (also archive attribute ) is a file attribute that is set by the operating system for newly created or modified files. Backup software can be signaled so that this file has not been saved. After a backup, the archive should be deleted accordingly and set again only after other changes. Thus, an incremental backup will be performed only with newly created or modified files, saving compared to a full backup time and space. The use of the archive bit but, for example, due to lack of write access to the files to be backed their limits.

Archive attribute and Windows

From Windows ( Save as ) is any modification, full overwrite automatically set and creating a new file, the archive ( there is at least one remarkable exception to Outlook Express and its DBX files). This can be supported by means of xcopy in connection with special parameters into account. The archive bit of each file is not set, if all the folders are moved. This poses a risk consistency if a backup is created only on the basis of this attribute.

Archive attribute and Unix / Linux

In the traditional file systems of Unix / Linux are not the archive attribute like it is not implemented. However, ZFS supports all file attributes of MS- Windows and therefore also the archive. To ensure the interaction of Windows and classic Unix file systems, DOS attributes are mapped to Unix file permissions. So Samba reached mapping the archive attribute on the misuse of the executable bits (X- bits). Analogously, the file system, and hidden attributes in the x -bit mapped:

Corresponding settings in Samba configuration file ( smb.conf):

Map archive = yes # x for the owner map system = yes # x for the group map hidden = yes # x for all Under UNIX, a backup of the date attributes is common.

Backup strategies and the archive attribute

Depending on your backup strategy, the archive bit is treated differently.

  • In the copy backup, so the burning data for backup purposes on CD or copying to an external hard drive, the archive attribute is mostly unchanged.
  • The Full Backup backs up all files - regardless of their attributes - and resets the archive attribute.
  • The differential backup backs up all files that have changed since the last full backup and therefore have a set archive bit. The archive bit is left unchanged.
  • The incremental backup will differ depending on the implementation in the respective backup program. So it may be that the archive bit is reset or not, as it is usually the case with daily backups.

Individual programs can fall back instead of this file attribute to other properties, such as backup programs that use md5 or progressive backup where file name, date and size are crucial. Generally one can say that modern, professional software, the archive bit supported but usually no longer work with it. In the corporate environment shadow copies are used (eg Volume Shadow Service, VSS) snapshots and progressive backup now.

Confines

The control of data backups failed on the archive attribute when multiple backup tools should be used independently for a securable system. This is often the case, particularly in larger installations.

Use of the archive bits requires that the reading backup tool converts the archive, so it has write permissions. If the backup plan provides that write access is granted only in the case of restore, the archive attribute can not be used.

Swell

  • File Management
75477
de