Source: zerofree Section: admin Priority: optional Maintainer: Thibaut Paumard Build-Depends: debhelper (>= 9), e2fslibs-dev, docbook-to-man Standards-Version: 4.1.3 Vcs-Git: https://salsa.debian.org/debian/zerofree.git Vcs-Browser: https://salsa.debian.org/debian/zerofree Homepage: https://frippery.org/uml/ Package: zerofree Architecture: any Depends: ${shlibs:Depends}, ${misc:Depends} Description: zero free blocks from ext2, ext3 and ext4 file-systems Zerofree finds the unallocated blocks with non-zero value content in an ext2, ext3 or ext4 file-system and fills them with zeroes (zerofree can also work with another value than zero). This is mostly useful if the device on which this file-system resides is a disk image. In this case, depending on the type of disk image, a secondary utility may be able to reduce the size of the disk image after zerofree has been run. Zerofree requires the file-system to be unmounted or mounted read-only. . The usual way to achieve the same result (zeroing the unused blocks) is to run "dd" to create a file full of zeroes that takes up the entire free space on the drive, and then delete this file. This has many disadvantages, which zerofree alleviates: * it is slow; * it makes the disk image (temporarily) grow to its maximal extent; * it (temporarily) uses all free space on the disk, so other concurrent write actions may fail. . Zerofree has been written to be run from GNU/Linux systems installed as guest OSes inside a virtual machine. If this is not your case, you almost certainly don't need this package. (One other use case would be to erase sensitive data a little bit more securely than with a simple "rm").