5.1 Using tar to Perform Full Dumps

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Full dumps should only be made when no other people or programs are modifying files in the file system. If files are modified while tar is making the backup, they may not be stored properly in the archive, in which case you won’t be able to restore them if you have to. (Files not being modified are written with no trouble, and do not corrupt the entire archive.)

You will want to use the ‘--label=archive-label’ (‘-V archive-label’) option to give the archive a volume label, so you can tell what this archive is even if the label falls off the tape, or anything like that.

Unless the file system you are dumping is guaranteed to fit on one volume, you will need to use the ‘--multi-volume’ (‘-M’) option. Make sure you have enough tapes on hand to complete the backup.

If you want to dump each file system separately you will need to use the ‘--one-file-system’ option to prevent tar from crossing file system boundaries when storing (sub)directories.

The ‘--incremental’ (‘-G’) (see section Using tar to Perform Incremental Dumps) option is not needed, since this is a complete copy of everything in the file system, and a full restore from this backup would only be done onto a completely empty disk.

Unless you are in a hurry, and trust the tar program (and your tapes), it is a good idea to use the ‘--verify’ (‘-W’) option, to make sure your files really made it onto the dump properly. This will also detect cases where the file was modified while (or just after) it was being archived. Not all media (notably cartridge tapes) are capable of being verified, unfortunately.

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