<!doctype refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN" [ <!-- Process this file with docbook-to-man to generate an nroff manual page: `docbook-to-man manpage.sgml > manpage.1'. You may view the manual page with: `docbook-to-man manpage.sgml | nroff -man | less'. --> <!ENTITY dhfirstname "<firstname>Thibaut</firstname>"> <!ENTITY dhsurname "<surname>Paumard</surname>"> <!-- Please adjust the date whenever revising the manpage. --> <!ENTITY dhdate "<date>February 6, 2008</date>"> <!ENTITY dhsection "<manvolnum>8</manvolnum>"> <!ENTITY dhemail "<email><paumard@users.sourceforge.net></email>"> <!ENTITY dhusername "Thibaut Paumard"> <!ENTITY dhucpackage "<refentrytitle>ZEROFREE</refentrytitle>"> <!ENTITY dhpackage "zerofree"> <!ENTITY debian "<productname>Debian</productname>"> <!ENTITY gnu "<acronym>GNU</acronym>"> <!ENTITY gpl "&gnu; <acronym>GPL</acronym>"> ]> <refentry> <refentryinfo> <address> &dhemail; </address> <author> &dhfirstname; &dhsurname; </author> <copyright> <year>2003</year> <holder>&dhusername;</holder> </copyright> &dhdate; </refentryinfo> <refmeta> &dhucpackage; &dhsection; </refmeta> <refnamediv> <refname>&dhpackage;</refname> <refpurpose>zero free blocks from ext2/3/4 file-systems</refpurpose> </refnamediv> <refsynopsisdiv> <cmdsynopsis> <command>&dhpackage;</command> <arg><option>-n</option></arg> <arg><option>-v</option></arg> <arg choice=req><replaceable>filesystem</replaceable></arg> </cmdsynopsis> </refsynopsisdiv> <refsect1> <title>DESCRIPTION</title> <para><command>&dhpackage;</command> finds the unallocated, non-zeroed blocks in an ext2, ext3, or ext4 <replaceable>filesystem</replaceable> (e.g. /dev/hda1) and fills them with zeroes. This 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.</para> <para>The usual way to achieve the same result (zeroing the unallocated blocks) is to run <command>dd</command> (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:</para> <itemizedlist> <listitem><para>it is slow;</para></listitem> <listitem><para>it makes the disk image (temporarily) grow to its maximal extent;</para></listitem> <listitem><para>it (temporarily) uses all free space on the disk, so other concurrent write actions may fail.</para></listitem> </itemizedlist> <para><replaceable>filesystem</replaceable> has to be unmounted or mounted read-only for <command>&dhpackage;</command> to work. It will exit with an error message if the <replaceable>filesystem</replaceable> is mounted writable. To remount the root file-system readonly, you can first switch to single user runlevel (<command>telinit 1</command>) then use <command>mount -o remount,ro <replaceable>filesystem</replaceable></command>.</para> <para><command>&dhpackage;</command> has been written to be run from GNU/Linux systems installed as guest OSes inside a virtual machine. It may however be useful in other situations.</para> </refsect1> <refsect1> <title>OPTIONS</title> <variablelist> <varlistentry> <term><option>-n</option> </term> <listitem> <para>Perform a dry run (do not modify the file-system);</para> </listitem> </varlistentry> <varlistentry> <term><option>-v</option> </term> <listitem> <para>Be verbose.</para> </listitem> </varlistentry> </variablelist> </refsect1> <refsect1> <title>SEE ALSO</title> <para>dd (1).</para> </refsect1> <refsect1> <title>AUTHOR</title> <para>This manual page was written by &dhusername; &dhemail; for the &debian; 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. </para> <para> On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL-2. </para> </refsect1> </refentry> <!-- Keep this comment at the end of the file Local variables: mode: sgml sgml-omittag:t sgml-shorttag:t sgml-minimize-attributes:nil sgml-always-quote-attributes:t sgml-indent-step:2 sgml-indent-data:t sgml-parent-document:nil sgml-default-dtd-file:nil sgml-exposed-tags:nil sgml-local-catalogs:nil sgml-local-ecat-files:nil End: -->