On Sun, 23 Nov 2008, Tetsuo Handa wrote: > What I wanted to do is "Zero-clearing *all zero-clearable* bytes". Other than acessing the fs directly with something fs-specific that knows how to do it, the following trick comes to mind: 1. compress all files to a tar.bz2. 2. remove all files 3. zero fs using dd to a file (will zero all blocks except for the ones used by the tar.bz2 4. unpack tar.bz2 5. remove tar.bz2 6. redo the dd trick. This will now zero all blocks that were in use by the tar.bz2. Of course, this only works if the (kernel, glibc, tar) are not writing random junk to the unused parts of a fs block. The cost is from 1 to 3 rm'ed inodes left behind. If you use two filesystems (i.e. tar to outside the filesystem), you avoid that possibility. > I wished there is a utility to zero-fill such bytes. So do I. And a IOCTL/syscall/whatever that we could use to sanitize (i.e. fill with an user-supplied byte) half-used blocks, so that we could have it on the most used filesystems (ext2, ext3, xfs, reiser...), and that we could implement scrub-erasing of unused filesystem areas properly. -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
