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-.TH "ZEROFREE" "8"
-.SH "NAME"
-zerofree \(em zero free blocks from ext2, ext3 and ext4 file-systems
-.SH "SYNOPSIS"
-.PP
-\fBzerofree\fR [\fB-n\fP] [\fB-v\fP] [\fB-f fillval\fP] \fIfilesystem\fR
-.SH "DESCRIPTION"
-.PP
-\fBzerofree\fR finds the unallocated,
-blocks with non-zero value content in an ext2, ext3 or ext4
-\fIfilesystem\fR (e.g. /dev/hda1) and
-fills them with zeroes (or another octet of your choice).
-
-
-.PP
-Filling unused areas with zeroes is 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.
-
-.PP
-Filling unused areas may also be useful with solid-state
-drives (SSDs). On some SSDs, filling blocks with ones (0xFF)
-is reported to trigger Flash block erasure by the firmware,
-possibly giving a write performance increase.
-
-.PP
-The usual way to achieve the same result (zeroing the
-unallocated blocks) is to run \fBdd\fR (1) 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:
-.IP " \(bu" 6
-it is slow;
-.IP " \(bu" 6
-it makes the disk image (temporarily) grow to its maximal
-extent;
-.IP " \(bu" 6
-it (temporarily) uses all free space on the disk, so other
-concurrent write actions may fail.
-
-.PP
-\fIfilesystem\fR has to be unmounted or
-mounted read-only for \fBzerofree\fR to work. It
-will exit with an error message if the
-\fIfilesystem\fR is mounted writable. To
-remount the root file-system readonly, you can first switch to
-single user runlevel (\fBtelinit 1\fR) then use
-\fBmount \-o remount,ro
-\fIfilesystem\fR\fR.
-
-.PP
-\fBzerofree\fR has been written to be run
-from GNU/Linux systems installed as guest OSes inside a virtual
-machine. In this case, it is typically run from within the guest
-system, and a utility is then run from the host system to shrink
-disk image (\fBVBoxManage modifyhd \-\-compact\fR,
-provided with virtualbox, is able to do that for some disk image
-formats).
-
-.PP
-It may however be useful in other situations: for instance
-it can be used to make it more difficult to retrieve deleted
-data. Beware that securely deleting sensitive data is not in
-general an easy task and usually requires writing several times
-on the deleted blocks.
-
-.SH "OPTIONS"
-.IP "\fB-n\fP " 10
-Perform a dry run (do not modify the file-system);
-.IP "\fB-v\fP " 10
-Be verbose;
-.IP "\fB-f value\fP " 10
-Specify the octet value to fill empty blocks with (defaults to
-0). Argument must be within the range 0 to 255.
-.SH "SEE ALSO"
-.PP
-dd (1).
-.SH "AUTHOR"
-.PP
-This manual page was written by Thibaut Paumard <paumard@users.sourceforge.net> for
-the \fBDebian\fP system (but may be used by others). Permission is
-granted to copy, distribute and/or modify this document under
-the terms of the GNU General Public License, Version 2 or any
-later version published by the Free Software Foundation.
-
-.PP
-On Debian systems, the complete text of the GNU General Public
-License can be found in /usr/share/common-licenses/GPL-2.
-
-.\" created by instant / docbook-to-man, Mon 31 Mar 2014, 15:41