summaryrefslogtreecommitdiffstats
path: root/source/a/zerofree/zerofree.sgml
blob: af6e3a5378b885731d919a2d2a2cb5f7779a11e1 (about) (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
<!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>&lt;paumard@users.sourceforge.net&gt;</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:
-->