The Scrub utility on Linux can accept different methods of scrubbing. These allow for different types and orders of 'passes'. For example, the 4-pass DoD 5220.22-M section 8-306 procedure is a 4-pass method where the passes are in order ofRandom0x000xffVerifyWhat is the scope of a pass? Does each pass write to the entire file / drive before beginning the next pass, or is the target for scrubbing divided first into blocks, and the whole 4-pass process is performed on each block before moving to the next one?
What constitutes a Scrub Pass?
linux;deleted files;delete
The scope of pass is one rotation of that pattern, from the start to the end of the object being destroyed then start another round with the next pattern available of that pattern group/method.Even not having explicitly said at docs(and I could not find at the source code any trace of paralel processing patterns), in a 379MB file, you can see that it passes on each pattern as a sequence. Using dod pattern group as an example:[root@host ~]# scrub -p dod filescrub: using DoD 5220.22-M patternsscrub: padding file with 744 bytes to fill last fs blockscrub: scrubbing file 398323712 bytes (~379MB)scrub: 0x00    |................................................|scrub: 0xff    |................  [root@host ~]# scrub -p dod filescrub: using DoD 5220.22-M patternsscrub: padding file with 744 bytes to fill last fs blockscrub: scrubbing file 398323712 bytes (~379MB)scrub: 0x00    |................................................|scrub: 0xff    |................................................|scrub: random  |.........................[root@host ~]# scrub -p dod filescrub: using DoD 5220.22-M patternsscrub: padding file with 744 bytes to fill last fs blockscrub: scrubbing file 398323712 bytes (~379MB)scrub: 0x00    |................................................|scrub: 0xff    |................................................|scrub: random  |................................................|scrub: 0x00    |................................................|scrub: verify  |................................................|I think it's safe to confirm that scrub will pass all patterns one after another the object being destroyed. 